swamp cooler

Would anyone here have any information, links to small swamp coolers? I'm living in my trailer and want to install a swamp cooler to beat the HOT Moab, ut summer heat and cut my costs over the A/C unit. The smallest downdraft I have found so far is 3k CFM and that's more then I need but the duct would fit perfectly over my roof vent where I would like to install one. I would remove the lid and the screen and it would be a perfect over the upper lip at 13-5/8". place a small wood surrund spacer under it and some plumbers tape straps up inside would be ideal. Anyone else done anything like this? Yes its freezing weather right now but I want to get the research done so I'm ready to go and time does fly. My calculations say I need only about 620 CFM. I wouldn't mind something at about 1k.

Thanks,
Mark

I have seen those before but had forgotten about it. I read on some other site of a guy who used one and it was marginal and would not always keep his entire unit cool (37 foot, no slides). They are also cost prohibitive for me so in all I have seen so far I'm thinking I will probably just stick with a good old traditional home style roof mount. I would rather overkill at 3k CFM that can be controlled with windows and a t-stat then to be too hot. 1/3 HP motors don't use that much power either, especially on low. Thanks for the reply.