MF Diesel 65 Thermostat Problems

I have a Massey Ferguson diesel 65. The original thermostat (Smiths England) no longer works and remains open. The parts catalogue lists the number as 890 991 M91. That cross references to a Vapormatic A-1446222M91. However, the Vapormatic does not fit. The outside edge is beveled on top instead of on the bottom. The Smiths is beveled on the bottom of the outside edge. Every tractor supply outfit I talk to says the Vapormatic is the correct thermostat, but it's not. Can anyone guide me to where I can order the proper thermostat?

If my photos uploaded, you can see the original is beveled on the bottom of the outside edge and the Vapormatic is beveled on the top.