You could try a repro, but if all its missing are the front mounting lugs, you need a bit of flat bar with some holes drilled in it to match the ones on seat frame and one for the mounting bolt, correct length can be provided, all you need is a drill and some beat over rivets.

If anyone could provide with measurements and the angle it sits at that would be fantastic as I don't have anything to work off.

email (option): chriscool@sky.com