This is where I obtained the ones that I got for my Q605 and they work fine. Shipping was higher than I would have liked, but they did package things well.

http://www.welovemacs.com/apple-memory-pre-g3-powermacs-powermac-8100-mac-512k-video-ram-simm.html

You could also post in the Trading Post area (if you haven't already)