You might check to see if there is a difference between those valves used in stationary structures and those in mobile (or manufactured) homes and RV's. Your local building code or building permit office should be able to give a definitive answer.
Remember to get not only the model number, but also the BTU input and output numbers, serial number, & manufacturer and model name of the furnace
. Once in a while there is more than one manufacturer for brand name products and slight changes exist among them.
Have you tried any heating/air conditioner/plumbing repair businesses? Bulk propane
(those who provide home delivery) suppliers often have repair facilities. RV repair shops aren't the only ones who deal with gas valve replacement issues. For liability reasons, it is not legal to repair most gas valves.
If it makes more sense (rather than taking the whole vehicle)--- take just the burner with valve attached to their shop. A substitute valve may be found, but be aware that the control knobs may not be in the same locations (sometimes that is an issue if they protrude through a panel).
Remind the technician...the furnace uses PROPANE
When removing the old set-up try to visualize if a larger or smaller size valve would work. The location of the incoming gas line. the position of the pilot gas line and thermocouple connection may or may not be issues.
If it makes any difference. valves for home wall furnaces are sometimes a little smaller than those used for forced air units.
We hope you and your Trill will soon be warm again,
& Ann K.