The following sites sell red/cyan anaglyph glasses:

Rainbow Symphony
http://www.rainbowsymphony.com/freestuff.html

Berezin
http://www.berezin.com/3d/3dglasses.htm

The Stereo Store
http://www.studio3d.com/pages2/store_glasses.html#ANAGLYPH

Disclaimer: this site does not endorse any of these merchants.
They appear on this page as the result of a Web search engine.

To learn more about 3D imaging:

Stereoscopy.com
http://www.stereoscopy.com