You can even use a "lamp dimmer" from Home Depot or Loews with a repti heater and it may be cheaper since otherwise you'll be paying for the "repti" designation. CHeck your discount stores first. It should be $10-11 there.
A thermostat is a tempature controller. you probally have one in your house you set it to make it hotter or cooler. But they have special one for reptiles that cost like $20 and work well.
For best price and inexpensive brand that has done very well for me, look for either "ESU" or "Alife" (they look the same to me) and try the on-line pet supply places:
lllreptile
BIg Apple Herp
Reptile Depot
Max Pet supply (I don't know if they have a website or just an ebay store or neither)
There are others too. Compare the prices of the item, add shipping and see what gets you the best deal.