This is pretty much one of the hardest cars to get off the shelf parts for. I know because I own one. Nothing is available in Australia (unless its already been imported from Japan).
Browse the Yahoo Japan Auctions for parts, and if you can find someone who is still trading get them to import them and pay the high price it now commands.
Rims all depends on what size you want. If you want 14" or 15" you can get similar things to what AE86/KE70 owners use. If you want 17" then you'll need to import, be lucky, get Simmons, or convert to 5 stud.
Coilovers most people just use the custom coil over kits you can buy from companies like Koni etc. Some people have converted the front suspension to S13 Silvia.
Body kits are non-existant in Aust. Import only.
They share all the same suspension and drivetrain parts as the MA61 Supra (and likewise RA65 Celica). Apart from that, pretty much nothing is compatible with any other Toyota.
Oh ya...its such a pain to get parts....just rebuild my GZ10 and been scouting almost a year now for parts....its almost done, since i have afriend in japan who also scouts for me there....its infact not that easy to even get it in japan...what kind of parts are you looking for...?