Someone sent me a shipping kit once that had unique cool packs.....
They are similar to bubble wrap except the bubbles in this case are gel filled. They are sized perfectly to fit underneath a cool coat. I keep them in the freezer. Once removed they will stay frozen for about an hour if kept under a wet cool coat. I have never looked for more but they are made by a company called Cryoflex. They work amazingly well for group showing.