Are Propane wall heaters safe for this?

What is a good VENTED propane heater that requires no electricity or is 12 volt?

There are a few out there. Perfection is a good brand as is cozy and several others. Most have an optional fan and I would reccommend a hydraulic thermostat over a milli-volt one. Most look like a square box covered in metal. They can be direct vent/sealed combustion or standard vent.