Old Skool Fastrax rims, I remember them.
As for other suppliers, have you tried Chris Rowcliffe, in case they have any old stock of Schumacher rims from the ballistic buggy molds.
I used to love my CAT 2000 EC, full carbon, alloy gearboxes, alloy rear pivot blocks, alloy screws, purple everywhere!!!
I think I've still got a Touring Car upgrade kit for a CAT 2000 (towers, and ickle shocks and body mounts)