Staying cool on the course

My main lesson learning from Chicago is that I cannot rely on race organizers to necessarily provide liquids or cooling services on a hot day. So, although I already have a fuel belt, and an amphipod, I am currently trying to decide which I want to get - a cooling vest or a camelbak.

I'm leaning toward the camelbak, but I don't want one of those little ones. I'm going to want to hold 2-3L of water. Screw the extra weight, because 4 pounds of ice water would have made a major difference in completing the death march on Sunday.

Any opinions or reviews would be appreciated.