Has anyone replaced the gasket on their FBH?

I bought a new (used) FBH, as my current one has a fault. I thought I'd clean the inside, and also check out what the sound of something loose inside was (it was s mall piece of carbon in the burn chamber).

I had bought what I thought was the correct gasket between the burn chamber and the blower assembly, but it turns out that it is completely the wrong shape.

I can't find the right one, and it doesn't seem to be listed as a spare part on the LR parts diagram.

Does anyone know either where I can get the correct gasket, or what the gasket is made of, so I can cut my own?