I made my own fan bus..after goofing around with electricity i found there not all that hard to build at all...
Basicaly what i did was take a small 12v power suply form radio shack to use as a testing power supply. Some old 80mm fans i had lying around and my rheostats. I goofed around with different wireing schemes until I found the one that seemed to work the best. And then implimented it into my PC.
Someday when i have time i'd like to make a picture of the wireing scheme for the one i built my self...but it's really not all that hard. You just have to keep your wires organized. And understand how fans run, how a rheostat works, and how a power switch works. I even got brave and added a led to mine now. hehe Once you get the hang of all the componets i'm sure you can build one with out a lot of trouble. and it will cost you a lot less too. rheo's are 3 bucks at radio shack, a toggle is 2 and small leds come in a big pack for a few bucks.