Yes, there certainly is, or at least there used to be. Don't know if they're still made and don't remember what they called them. Back in the 1980s we had one on our 22' LazyDaze. They installed them because they ran on 12-volt and were supposedly good for boondocking. Also, being built in the southwest, it was assumed (wrongly) that they would be used in desert areas in which case air conditioners weren't as good. To be honest, it wasn't all that great and really didn't work very well as we traveled around the country to more humid areas. I remember boondocking in Boise ID at a friend's house and it flat out did not cool anything. In fact, it was useless. We were glad to have the air conditioner on our next unit. They're much more effective! Yes, you need 110 to operate one but most campgrounds can handle that. Also, most motorhomes now have generators which we didn't have back then - strictly batteries and solar panels to charge!
We have a permanently mounted swamp cooler to cool the garages in our stick house and it works great when the humidity is low. But during the monsoon season we often turn it off because it just doesn't work when the dew point gets too high. You're far better off with an air conditioner.
ArdraF