i've had fantastic fortune at retrobike and london fixed gear forum classifieds.. BF also has a good c&v classified section.

http://www.bikeforums.net/forumdispl...-Vintage-Sales

http://www.retrobike.co.uk/forum/viewforum.php?f=22
http://www.lfgss.com/forum6.html

i will echo the above statement that you should start with a frameset that is worth building up, which you can also find on those sites.