Putting hot water in plastic soda bottles works too. I have a cheap styrofoam cooler that I can put 6 to 8 20oz bottles filled with hot water at the bottom then cover that with a towel. Put the snakes in pillow cases, lay them in and cover with another towel. They stay nice and snug. This works well for emergency transport.

I also have 40 hour heat packs for an emergency.....