The Hydropharm thermostats are around $36 on Amazon . Some people have had bad luck with them.
I have 4 of them, 2 have been running for 3 years with no problems, and my temps are right on.
I also have a Herpstat Intro .... these are only $99, and they are proportional instead of off/on.
The problem with the Hydrofarm is that it fails wide open. If you get one put a lamp dimmer between the t-stat and the heat. Set the lamp dimmer so the heat can't get over the mid-90s, and then if the t-stat fails your snake will be uncomfortable but not burned.