I've seen them at Wal-Mart too and I'm sure you could get them at a sports store, I use them in my snowboard boots and I've picked them up at sports places. If you run into an emergency and have no heat source at all, I've heard some people will start the car in the driveway and sit in the heated car with the herps for a while... I don't know though, taking reptiles outside probably isn't a great idea.