It's a bit of a tricky one as there aren't a massive number of them out there (the general consensus seems to be 70-ish Model 70s surviving), but that includes quite a few which are basket cases which realistically are only good as parts donors. They seem to pop up for sale in fits and starts...values...well I've no idea. They just seem to be all over the place, but in general do seem to be increasing. I think the popularity of Hubnut's escapades with TWC and demonstrating that they're a lot more capable than reputation would have you believe has done a lot to raise their popularity - plus it's finally getting the message out there that they are NOT illegal to drive.
This is probably also why it feels like more have popped out of the woodwork in the last couple of years than in the past.
While I've had one for a few years now I'm afraid I don't really have any good contacts where finding one is concerned.
I'd keep an eye open (worth setting up a saved search) on eBay and watching the usual classic car sites. If you're patient you'll probably find one.
If you're looking at one, the bodywork is the most important thing unless you're handy with glass fibre and have the facilities to do repairs properly. Replacement body panels aren't available and nobody has made moulds for anything *yet* though we are hoping to improve on that situation at some point...they tended to get bashed and scraped a fair bit in service, but spending a couple of decades in the back of industrial yards, farm sheds etc won't had helped either. There's zero support framework under the nose so it's easy to take huge chunks out of there. As TPA showed when I got her.
The rear apron below the engine cover is a favourite for getting smashed to bits too. It gets baked by the exhaust as well which tends to make it even more brittle. This was outright missing on TPA.
Most cars had aluminium floors fitted while in service but it's not something that's guaranteed. This was because their weatherproofing is...well about on par with a Series II Landy with a canvas roof...and water tended to get trapped under the rubber floor mats, so fitted the panel from the inside out. The floorpan however is NOT structural, so aside from having to pull the seat and gear selector out sorting it isn't a bad job. In my case it had been very poorly fitted with pop rivets!
Structural rust is *rarely* an issue. I've only heard of one that's seriously rotted and that spent its life a stone's throw from the North Sea. The rust proofing they used on the chassis on these things was very effective.
There are two areas that do rust for fun, one is the metal window frame on the doors. It's just screwed on by a couple of little tabs, and water tends to get trapped under the window runners and rots those out. Repair isn't impossible, but fiddly. If you've got access to a proper fabrication workshop it probably wouldn't be that hard to make new ones. The second is the fuel tanks. The original tanks had a lip around the top of the tank where water collected. At some point they switched to a slightly different design which was better - but they can still rust.
Doors aren't particularly sturdy. The handles pulling out of the fibreglass (both interior and exterior) is a common issue, and it's not uncommon to find the inner and outer skins separating around the edges.
Hard to get bits.
[] Fuel tanks. As mentioned above they rust. I've not seen one available for sale since I got involved in these cars three years ago. I had a new one made up using the original as a template by Fusion Fabs over Oxford way, cost was £250 & VAT which for a scratch built ally tank I thought was absolutely fine.
[] Carb overhaul kit. These are usually fitted with a Weber 32ICS10 carb, for which spares availability isn't great. I'm absolutely sure another carb could be made to work with some testing though.
[] Exhausts. There *are* still a reasonable number of NOS ones floating about out there from what I've heard (nothing verified though) but they don't turn up often. It's quite a complicated bit of metalwork because it also includes the heat exchanger for the cabin heater. This is also why it's not a good idea to do welded repairs...if the outside is failing the inner tubes for the heat exchanger aren't likely to be far behind. I think given how cheap they are these days having a CO alarm in the cabin would be a common sense addition. I have one hidden under the seat (so it's near the cabin heater vent.
When mine starts to show signs of old age I'll look to get a stainless system made up, probably by the same guys who did my fuel tank. I'll see what the price is and whether getting a few made at the same time would make sense as I'm sure other folks wouldn't say no to one in stainless.
[] Any body panels.
[] Rear wheel hubs. Well. Sort of.
The hubs are Fiat 500/126 parts, but modified at the factory to suit the Mini wheels (so a 4" rather than 100mm PCD), and with non-standard wheel hubs fitted. The studs are quite weedy, and are unobtainable themselves...so I'd suggest finding an engineering shop who can drill and tap it to take 3/8" wheel bolts. That's my plan for the future.
[] Centrifugal clutch shoes. I know where two sets are, having surfaced in other boxes of Invacar parts but haven't seen any for sale individually. Getting them relined is usually the easiest solution.
[] Throttle cable. Sounds silly, but it's something like 4.5 metres long. Dead easy to get made up by the likes of Speedy Cables, but you'll be very lucky to find one long enough on the shelf that's long enough. None of the "make it yourself from a 10m reel" kits I've had contained the right end to hook up to the twist grip.
[] Glass. It's all bespoke, though at least is flat so getting a specialist to make it up if you can find a template shouldn't be hard...albeit expensive.
Most of the rest of the car is either just parts bin items or stuff which does seem to pop up now and then. Engine wise there's still good support from a marque specialist, the CVT pulleys can be sourced from Comet who took over Salsbury though some NOS sets still seem to pop up occasionally. The CVT belt itself can be replaced with a Dayco HP2020 (which is usually cheaper to get shipped from the US where it's a common fitment on ATVs.
The actual gearbox itself is bespoke, but I've not heard of one failing so far.
Hopefully that ramble contained something useful...sorry I don't know of anyone selling one just now though.
Definitely worth patience though. I've been astonished by how competently TPA handles the job of being an actual car, and possibly even more so how much fun she is to drive.
If I do hear of one for sale I'll try to make sure it's linked to from here.
Ax GTi Turbo