This is not the correct clamp, though it looks like some of the original brass parts are there. Here's the clamp illustrated in the 1940 parts book:
We can make one of these. First we will make a card template.
Clamped to a piece of 14 SWG cold rolled sheet ready for marking out
Cut & filed to shape
The clamp formed and ready for bending. The long centre section is now curved across it's width and the ends have been folded up
Bending the clamp - I'm doing this hot.
Fitting it for the first time reveals it is about 3/8" too short:
In principle the design is sound. I've run the bike with the clamp in place and the exhaust pipe joint doesn't leak.
We'll just have to make a longer one.