I have seen these bags sewn in all types of sizes and shapes. Use your imagination. Just be sure to supervise your kids while they are heating them up. Here is a link to an idea to use a sock for the rice bag.
Watch for my upcoming post called “Traveling Teams 101”. It will give some ideas of how to save money on food as you follow kids to their various games and events…I had to do this post on the rice bag first so you can have a rice bag to keep your food warm at ball games. 🙂