I agree with Andrew on Radio Shack, and yes, the units from WalMart only read humidity on the unit itself, not on the probe, but humidity doesn't have to be as tightly controlled as temperature and if your humidity is good on one side of your enclosure, it should be good on the other unless your enclosure is way too big for a ball python anyhow. Wendy, welcome to the forum, and if you have a WalMart nearby, that's probably your best bet. if not, I would check hardware stores as being a likely place to carry digital indoor/outdoor thermometer-hygrometer combos without charging ridiculous prices for them.