Sorry, I'm without a digicam but have attempted a pic below.
I just use two different types/sizes of "O" ring.
Two of the small 1.8mm section black ones ("Nitrile", I think) and a larger 2.6mm section orange one at the base of the exhaust outlet. This one is "Viton", if I recall, but I could have the two materials mixed up.
Anyway the smaller ones prevent the metal to metal contact mentioned and the larger one takes the compression forces from the exhaust spring.
The "O" rings are particularly tough and you can happily use two manifold springs that would normally just separate the flange part from a normal gasket in a couple of heats.
They are still affected by fuel etc. but last a whole lot longer than the normal silicone ones. I buy these at any local bearing supply and they're a few dollars for a handfull.