For a low cost, low tech way to power a fan, I might suggest looking around at Goodwill, Salvation Army, etc. Remember all those little transformer power supplies for all those gizmos we use? Some of those are 12V DC and run small fans fine. Just match the fan to the power supply. If you find a power supply with the same voltage as the fan, just make sure it is rated to put out enough power to run the fan. Search for electrical conversion calcs on the net. You may want to convert milliamp to watts, etc. but the calculators will do all the work for you.