With her involved in so many great sports, riding bikes and just being out going we have had our share of ice packs. So out of necessity we have started to create our own ice packs to keep on hand.
1 cup rubbing alcohol
3 cups water
Mix the two together in a gallon size ziploc. Freeze and while the ice pack will be ice cold the alcohol will allow the liquid to smush up and move around. Not freezing solid helps to keep the ice pack usable.
The next best thing to this is a bag of frozen peas. you can break the peas apart and then it will conform to where you need it to.