Both of these are web pictures but the bottom one is identical to what we built . We bolted the door and vent on and used an old grill grate inside .This is going in a 27 Ft. trailer so it should heat it up nice.
You could build a heater like this from any 20 ,30 ,40 lb. or larger empty propane tank do a web search lots of ideas available .
Here is my BBQ smoker its nothing but a 200 gallon oxygen or propane tank .
All we needed to make our heater was a sawzall and drill .A large hinge and exhaust flange and bolts and nuts.
I have an old air tank that I think will make a nice medium /small wood heater just to keep in the shed just in case . I may make it a little more elaborate with a cooking plate and a small oven mounted on top.I have to admit I am now hooked on fresh bread and want a way to bake in any event !