Let me start by saying Much respect to you guys who work in that. I don't know how you guys manage doing that daily.
Have you tried "Florida Water" ??
http://forums.finehomebuilding.com/breaktime/general-discussion/recipe-florida-water-keep-cool
^ that is the only link I can find on the quick. Basically you add just a bit of it to cool water, dip a rag in it and keep the rag around your neck. The "Florida Water" evaporates more quickly than water, giving it even better cooling properties. Think of it like menthol for your sweat. Sounds kind of crazy, but works like a champ.