Try http://www.mgreptiles.com/index.html they have a great selection of thermostats. If its a glass tank i'd use a stick on heat pad on one side (it's easy on a glass setup) connected to the thermostat and the probe of the thermostat can be taped on the inside of the glass were the heat pad is. Also get a digital hi/lo thermometer with a humidity monitor and also tape the probe to the same area so you can monitor the temps and adjust the thermostat as needed. I've used all kinds of thermostats and now use the Herpstat line exclusively. They are pricier but far superior. Mosts thermostats turn the heat pad on 100% and they crank up and pass the temp the shut of and cool fast (either on or off). The herpstat thermostat gradually increases and decreases amount of power to heating device (10%, 20%, 80%) as needed to keep steady control and not too much then too little. Hopr this helps. Don't use rheostats they don't measure temps accurately. Heat bulbs and overhead heating do dry the air. High light can be stressful to BP's. Undertank heating is best for BP's.