Here are the sources I frequent

http://rayeveritt.com/ - Perfect for hoses, fittings, and misc parts.
http://www.nostalgicairparts.com/ - Receiver/Driers and mount kits. Check out their underdash evap units.
http://www.ackits.com/ - Condensers and Seltec compressors, although lately I have been buying them from eBay in December and paying $50 for new Sandens.

There are plenty more sites out there but I always fall back on these.