If you think you might like to try to make your own misting system on the cheap, check out these instructions for how to Build your own PVC mister. The mister shown is meant to be for cooling off a pet, with only one mister nozzle. And it uses the cheap plastic mister nozzles. But the design could be modified to use more reliable brass and stainless steel mister nozzles.
If your dog suffers from hot weather like mine you can build this PVC pipe mister for about $10.00. Construction only takes a few minutes after you have all the required parts and tools.