if you need a cheaper but decent thermostat I have been using this one from amazon and it works awesome. keeps the heat withing 2 degrees of where you set it
http://www.amazon.com/Hydrofarm-MTPR...529750&sr=8-14

there are better more pricey thermostats if you wanna pay 100+ that would probably have a longer life span but if money is an issue this one works great for 1 UTH