Is your garage detached? If so, this might be a good option: https://www.homedepot.com/p/US-Stove...E&gclsrc=aw.ds
Just add a 55 gal drum and stove pipe.
Another option is to check the local propane service and see what's the smallest tank that they'll come out and fill. Check CL and find a good used 100 gal (or whatever) tank, some copper tubing, and a wall mount Catalytic heater and you're in business!
Check local codes and homeowners insurance requirements first. Many more options for detached vs. attached garage.