55 5T seat bracket

I am working on a 1955 5T Triumph Speed Twin and just got a new seat for it. When I got the bike it had a solo Bates seat. What I'm looking for is the correct seat mounting bracket. What is the part number for the bracket? I have the parts book and I don't see a listing for the bracket and of course there is no illustrations.

Thanks for any help you can give me.

John in Texas

Looking at the parts book it says the seat comes with the mounting hardware. The after market seats of course don't.
I spoke to a guy who is willing to take the seat off his bike and send me pictures and measurements.