old computers! rip them out strip wire, find old old old cell phone charger cut end of that plugs into phone....strip them as well connect + to + - to - with wire nuts or electrical tape. use as exhaust or a fan to move air around in the cab.
visit some scarp yards or flea markets to get old pc's... shit u might even find the fans already removed for you!
and if u want to buy it to know all the ratings and stuff just go to newegg.com! cheap cheap there ...or amazon id recommend. go to a coinstar do free coin counting for amazon gift card. bring a 20 dollar bill and get 2 rolls of quater...put them in coinstar and it will be enough for the fan and shipping.