Bountyhunter,
You can get surplus Espar, Eberspaecher, Swingfire with Turboheater that was used in NATO military Unimog vehicles, a survival vehicle if I ever saw one. They only need electricity to start. Once started they nolonger need electricty. The exhaust gasses are used by the turbocharger as a blower. They can be obtained in either gas or diesel versions in either 12 volt at 12.5 amps or 24 volt at 6.25 amps. They even have their own fuel tank. They are also portable and can be setup to heat a small building, i.e. shelter. Factory rebuilt units can be had for less than $200. You can usually find them on eBay from time to time. These are very safe units that military grunts have used for years.