The following suppliers are known to be able to supply parts for gray-market cars.

• Maximillian Importing, http://www.bimmer.com, (800) 950-2002. Direct importer, Mobile Tradition contact for North America. Any model, any part still available from BMW in Germany.
• Bavarian Autosport, http://www.bavauto.com, (800) 535-2002. Mostly 323i hard parts. Free catalog available.
• BMP Design, http://www.bmpd.com, (800) 648-7278. Mostly 323i hard parts. Free catalog available.
• Korman Autoworks, http://www.kormanfastbmw.com, (910) 275-1494. Mostly 323i performance and racing parts. Free flyer available.
• KSK Distributing, http://www.quikpage.com/K/kskalpina/, (818) 843-2620. US Alpina distributor. The only US Alpina source, and they do acknowledge that e21s stillexist!
• Circle Tire Company (they don't sell tires!), very knowledgable on older BMWs, even gray market. Contact Michel Potheau.
• CNPR, http://www.justbmws.com.710 Turquoise St., La Jolla, CA 92109, (800) 466-8184. Baur parts and info.
• Your local BMW dealer. Regardless of what you may have heard, some dealers are not put off by gray-market cars, and BMW North America actually stocks some euro-only parts. My local dealer even has a euro parts micro-fische for e21 323i's and has had no problem ordering parts for me. Give it a try!