These are adapters are used for just about everything...

We're talking about the ones that you plug into the wall... and where those two electrical prongs are located, there's a small solid, heavy plastic box. That's the adapter.

These are used for small computer speakers... cordless phone base power... If you go to Radio Shack, ask them for a "AC to DC" adapter... How many amps? Small.... 1, 2Amps... maybe 3...

Volts? Well, your computer fans run on 12volts... so that would be the best to pick... but you can really hook up 9 volts... 5 volts.... etc.