The vet actually said that they can handle the cold for a short amount of time. Thanks for the advice!We put our temp sensitive animals in coolers with hot water in plastic bottles, The animal in a box, inside the coolr, so they never touch the bottle. It works for frogs, inverts, and reptiles.
That aside... I put Medusa in a bag inside my shirt when I bought him home in when it was really cold. And I don't have a car, so it was bike - train - bike.