When my power went out one winter I put my snake in a critter keeper and kept her under the covers with me! It wasn't ideal of course but it was warm enough that I didn't have to worry about her getting sick. As far as hand warmers go, be careful with them, some of them get very very hot and could cause accidental burns. They also last a long time so I don't think you'd need too many to keep a pac warm, maybe even a single hand warmer would be enough.