Consider checking Ebay. There's someone on there who is frequently selling pairs of UTH's for very little money including postage. I've bought from her twice and it's worked out well each time.
Petsmart carries both ESU Thermostats and thermometers. Not sure on price range for the thermostats, but i just bought another thermometer the other day for $8.
I agree it is easier to get scammed on ebay. You have to always check feedback when buying. make sure If you are buying used that the seller offers refunds. I buy from ebay all the time and have had very little problems. Most people will do all they can to keep you happy because they do not want you to leave them negative feedback. It's a risk but if you have a problem a good seller will usually work with you.