You might have had one of those goofily expensive CheapHeat systems.
It's $1,000 for the near equivalent of a $15 milk house heater that blows through your existing propane heater vents.
It's an easy add on if you think you'll offset a couple of thousand dollars of propane.
https://www.rvcomfortsystems.com/cgi-bin/buy_new.cgi