A European company called Ebersbacher makes this type of unit. They also
have a US subsidiary, don't know the location, though. Fans of the really
old Beetles and Porsches will recall the gas burning heaters that were
available on those cars. Same idea, more primitive technology.
Gas burners are available in the US; some motor homes have them fitted.
A more up to date solution would be one of the so-called "heat batteries."
It is a latent heat storage unit which has been touted in the press in the
last two or three years. Saab showed them, so did VW and a few others. I
have heard that BMW will actually offer it on the new 5-Series.