Hey, I know finding heaters (and affording them) can be hard. Just wanted to let people know that the website Kens Fish - Home of quality tropical fish food and supplies
is currently having a sale on their Hagen Elite heaters; the 25w is adjustable and fits nicely into most tanks 1-5g. If you are having trouble finding a heater in a store near you, you might consider ordering one. It's winter in the Northern hemisphere so our bettas need to stay warm. :)
I have ordered from this website and it's a good company. Tip: order an extra thermometer because while adjustable, the Elites don't have actual numbers on the dial so you need a thermometer to monitor the temp.