Maybe something like this? http://www.bigfogg.com/corral-cooler-misters.html
Talked to a guy on YouTube who has had his one of these for over two years and only had one disc break. That's the unit he bought. He has a video of his GH fogging up which is pretty cool, so I think I may get this and a timer. He said it only uses 10 gallons a day on a hot summer day. Since it is floating, I can put it in any sized container, so I can just put it in a big tub.