I have an Aquaview 360 from Walmart (about 30 bucks for a 3 gallon. A 2 gallon might be a few dollars cheaper). The heater I bought was from PetSmart.
This one, if I'm not mistaken: http://www.petsmart.com/product/inde...ductId=4134008
I got the 10W one, and it's been in the aquarium for a couple of hours and the water is now optimum temperature (it was 68 degrees before I put it in there). I got it for about 18 dollars.