Portable heat?

I am bringing my ball python for a "check-up" at the vet next week, just to make sure he's clean and healthy. Now I live in Massachusetts, and it is obviously very cold here, and not knowing what the weather will be like next week, when I bring him should I put a heating pad in the bag I'm bringing him in? Now, I have a plastic container with holder that he would be in, then I was going to put the container in a bag to keep the cold air from going through the holes. I just don't now how long we'll be out and I don't want him to get cold. Should I use the UniHeat pads, or like hand warmers, or something? Advice would be much appreciated :)

When i've taken mine to the vet in cold weather - I found the best way for me was to put them in a bag and then put the bag inside my coat - that way the keep warm by your body heat.

Make sure you warm the car up really good also.

Hope this helps.

We have the same problem here in Sweden.
I use a styrofoam box that I put two bottles with warm water in, then I just use a snake bag or some container and places it on the bottles.
Hope you understand what I mean, I´m not that used to write in english ;)

Both are very good ideas, thank you. :)