Not that I want to endorse Walmart or anything... it's actually hard for me to navigate because of the lighting and the sensory overload.
But if you can make it through to the camping section, check out their Aqua Cool neck scarves. They're filled with some sort of water-soluble silica. Soak them in water for five minutes, then put it in the fridge. Tie it around your neck, and you've got a great way to cool off on hot days. I've just been to the Kerrville Folk Festival, and it really helped me survive the heat in Texas. (that, and soaking in the Medina river in the hottest part of the day!)