The key to misters is making sure they don't put out too much volume. You don't really want to keep your cattle soaked all the time, you want most of the mist to evaporate - that's where you get the cooling. You can put together your own from the sprayer parts available at your co-op or farm/ranch supply, just be careful to get nozzles that put out a fine mist with low volume - you might even have to have them special order it for you. Of course the misters sold by the show suppliers or as patio misters come with that kind of nozzles, and can often be bought cheaper.