Check out the Wave propane
Olympian Wave 3 LP Portable Gas Catalytic Heater by Camco (3000 BTU )- Can Warm Up to 130 Square Feet of Space
They come in different sizes. Many people swear by them. Some people say you can use in an enclosed space, but please don't, keep a window open.
We use an electric space heater when hooked up to a camp site with electricity.
works well but is noisy.