Zoo-Med makes a cheap thermostat called the ReptiTemp 500R. It is worlds better than a dimmer but not as good as a Ranco or even better a Herpstat/Helix. Yet it gets the job done for only 30 dollars. If on a budget this tstat is GREAT. Been used as a QT thermostat and when used on the Burm when he was in the closet. It takes a bit to dial in (1 to 2 hours) but after that it's golden.

Only downfall to this thermostat is that is a on/off and a power set thermostat. So the dial is not a temperature, it's the amount of power going to the unit as when the ambient temps drop the hot your heating drops with it. Unlike a Ranco or higher grade thermostat keeps the temps at the temp you set it.
Example my herpstat is set at 90 and if the heat goes out and the ambient drops to 60 my hot side is STILL 90 degrees