1. For my frog tog, I add a few squirts of Sea Breeze to the ice water. It is an astringent that somewhat resembles spirits of ammonia. You can get Sea Breeze at Wal-Mart in the skin care section. It is refreshing and I would swear it helps keep the ice longer in the cooler.
2. For the really hot plate games, I have a "chiller vest" made by GlacierTek at
The Original Cool Vest - Body Cooling Vest Ice Vest - Glacier Tek. I have the Concealable model and I swear by it.
It looks like a bullet-proof vest and goes under the chest protector. It has four sleeves on the inside- 2 in front, 2 in back. There are four "cooling elements" that are clear plastic bags with a high-tech liquid inside.
Place the elements in your cooler ice water and in 20 minutes they become solid. They will remain at 59 degrees for 2.5h in 100 degree temp. It reduces your core by about 15-18%, respiration is down, heart rate is down, perspiration is damn near zero. You are less-fatigued afterwards.
After the game put the elements back in the cooler and they are ready again in 20 minutes.
It weighs about 4 pounds, but you don't even notice it.