If you just have the one snake put him in a pillow case, zip tie it closed, and put him down the front of your shirt to keep him warm.
At night put him in a bin (still in the bag) and put him under your bed covers with you. The bin will ensure you (and any other pets you have like dogs and cats) don't roll onto or step on him.
If you have a BBQ, camping stove, or even candle heater, you can boil water, fill a metal bottle or flask with the hot water, wrap it in a towel, and use it as a warmer. You will just need a way to keep your snake from coming in direct contact with it.