Hey i just stubble across this topic looking for something else but a little feed back on this. If you have a solder iron or gun and want to do it yourself use 5v fans and take a old or cheap usb cable and slice it up and solder it to the fans. Red to red, black to black, green and white you can trim off. Then get yourself a USB power bank. A 2600mAh power bank that you can get almost anywhere for about 5 bucks will run 2 fans for about 6 hours. And the best part is no more wasting money on 9v or AA batteries because they are rechargeable and you can use it to charge your phone when you are not trooping.
If you dont want to make it yourself I sell some here
-----------