We need to find a low cost air conditioning system for our cars. These cars run only 250 cc engines or electric which cannot power an air conditioner. We need perhaps a roof mounted unit that can sit on the top and run through an inverter. Like is made for truck cabs when the truck is parked and engine not running the cars are small so about 500 btu or less would be plenty. Any manufacturers or suggestions most welcome, orders could be in humnderds and hopefully thousands. Trident tricars and electric city cars.