Get one of the mini sized metal trash cans with the lid. (5 gal I think.) Place four large lag bolts into it about 2/3 of the way down. Make sure they are level. Drill several small (1/4") air holes around the bottom edge and in the lid.
Take one of these:
And place it in the can on top of the bolts.
Drill two 2" holes on opposite sides of the can as close to the top of the rim as possible. Buy two of these:
Bolt them on the _inside_ of the can at the place where you drilled the 2" holes.
Connect them with exhaust flex pipe:
Attach an inexpensive 12V muffin fan to the outside of one of the flanges and power that using a 12V battery or brick or whatever.
Now at the bottom of the can, exactly in the center, place a large can of gel alcohol fuel - aka Sterno.
Light said Sterno. Sterno heats the radiant flowerpot heater, which heats the flex pipe, which heats the air that the fan blows. The pipe prevents the forced air from possibly disturbing the alcohol flame among other things.
For extra points wire in a thermostat to the fan circuit.
Cross-posted from Dreamwidth ( http://nimitzbrood.dreamwidth.org/279656.html ) but feel free to comment here as well.