you should be able to pick it up in a local headshop, although I've heard that it's not available in several states.

the pack that is included just needs to be shaken to be heated... but to be honest, i don't know how good of a job it does when heating the urine from room temperature. it's always best to heat it in microwave first for 9 seconds, tape the heat pack to the bottle, and then stuff it in a warm hidden place.