How old was the heater? If it was relatively new I'm sure you could get a new one from the manufacturer or even the store you bought from. At the very least, Walmart sells pretty cheapo heaters for up to 60 gallons for like $20 until you can afford a new one. Heck, if you buy online you can get an Aqueon heater, a much better brand, for about the same price.
If you are totally broke, go to a fish store in your area, tell them what happened. They may have a used one you could have. Lots of time, they get aquariums and all the stuff with them in exchange for bigger ones or just given to them, if they take them out of the people's house. They usually throw away the stuff like heaters or sell them dirt cheap.