You could also have a powered cooling blanket which would work for as long as you have power and doesn't require the environment to be colder than you. Most people don't like to go around wearing their refrigerator, I don't think, but one could make something a lot smaller with Peltier devices.
Written by Rex Kerr
One who rejoices when everything is made as simple as possible, but no simpler. Sayer of things that may be wrong, but not so bad that they're not even wrong.