I use a water bath to heat hide glue and keep it warm. They use these in scientific labs to maintain a constant temperature. It will go up to 100 degrees C (boiling point of water), and works like a double boiler. That said, I imagine you could fill it with wax instead of water. The melting point of paraffin is 56 degrees C (according to Google). Mine heats the water in a few minutes and maintains the temperature spot on.
I got mine off eBay as a used item. A
search brings up a lot of these at varying price ranges and sizes.