I was at Wal Mart in Hilliard last night and they have catalytic heaters for $10. It is 880 BTU heater with a carrying case, 2 thermal blankets and waterproof matches. It would the perfect size for shanties.
Heres a link to a search of cabelas "propane heaters"
The Coleman Power Cat looks like it would be perfect for a one man shelter!
I like the fact that it has a fan to blow the warm air out. Probably enough to take the edge off any cold air, huh? Super small size, too.