Amazon delivers:
http://www.amazon.com/Zilla-11403-Co...dp/B0018CLYNG/

So does Reptile Basics:
http://www.reptilebasics.com/thermostats

This is the single most important piece of equipment for your snake. If your ball python is too cold it won't eat because it can't digest its meal. If it's too hot that can also stress it into not feeding, and if it gets over 105*F you risk neurological damage.