I would think any of the digital thermostats from your local hardware store would work. If you are just running your furnace look for one which is furnace only. If you need to control both the furnace and the A/C, those are also available. The only one I think would be hard to find would be Furnace/AC/Heat Pump.
Craig and Carol
1997 34' Excella 1000
1970 27' Overlander, International
2009 Ford F150 5.4L
ProPride hitch with 1400# bars
Past President Southeastern Camping Unit (12)