My recommendation would be to have an AC Mount & Power put into the trailer then buy and install the AC yourself. It "should" save you a couple of hundred bucks, but will be up and out of the way, be setup to handle the AC much better and won't be a rigged setup that something could go wrong on. You can shop online for the right AC unit for you, easy to find some links and various price ranges, but IMHO will serve you better in the long run.
Oh, and if you do go this route, take into account needed head clearance around it. Just FYI
Border War Smokers - "BBQ worth killin' your neighbor for"