Yep - I do the hot water bottle trick all the time when taking snakes to shows in the cooler months. I use a small cooler and place the bagged snakes on one side and the bottle on the other. Or I put the bagged babies in small bags then put them in a 6qt shoebox. I can stack two boxes in my cooler and then put the hot water bottle on one end of the cooler. I try to give them enough room that the can move away from the heat if they want.