Idea Exchange: Do-it-yourself ice packs
True ice packs are easy to find, but because they are a block of ice, they are not pliable. So I use a mixture of 50% rubbing alcohol and 50% tap water instead. The rubbing alcohol prevents the water from completely freezing, allowing for a malleable ice pack. Party balloons and resealable plastic bags work well to hold the mixture.
Dr. Michael Rader