I am also looking for a thermostat for this particular furnace. My grandparents have this furnace in the old modular home that they live in. I have replaced the thermostat with several different types and cost values, but my grandfather says it does not work proper.
Since I work at a community college in the skilled trades division I have spoke to several of the HVACR instructors about this. They have all given me several different thermostats and said that this should work, of course according to my grandfather they have not. If I find out anything I will let you know.