eBay is perfect for cheap CD / 32X systems.
I wish I could find more games for reasonable prices though. One day at my local thrift store though, I found two games for the Sega CD, complete and in good condition for two dollars each; Tomcat Alley, and Guy-We-Break-Up-Over Vs The Kingpin.
(btw, I'm forbidden to say that superhero's name, so just assume)
Just be sure to look everywhere, Linkin800.