You don't mean a "natural gas" tank you mean an LPG (propane) tank. They are related but different animals. Frankly if you don't want to spend that money, a wood heater is about your only option. Are there emissions regulations there for wood heaters? If not you could even build one. You used to be able to get a "kit" (door and legs) to make a wood heater out of a barrel. TWO barrels works well, 1 on top of the other But then you need wood, and I've no idea what your supply situation is. Can you get firewood there reasonable? Do you have your own on your property?