Ace and Speedtech still has some stuff, both Penguin, Kawahara, and Mugen Upgrades. Keep you eye on Ebay. Here is a link to ACE, and Speedtech. I also believe that Castle hobbies carries a good lot of Kawahara stuff.
http://acehardwarehobbies.com/2.2/ca...4b7192438ae0a8
http://64.70.208.72/speedtechrc/64.html
Tom