Incubator need a fan?

You can get computer fans that are anywhere from 5v - 12v, but most are 12v. The DC wall transformers are expensive at most stores like Radio shack, but you can get them for a few dollars online. The front of the fan will tell you how many volts and mA your power supply need to be. Most fans will run (slower) on a slightly lower voltage, but pay attention to the Amps. Here are a couple of older links with some sources.

http://ball-pythons.net/forums/showthread.php?t=62212
http://ball-pythons.net/forums/showthread.php?t=61908