This Instructable will show you have to make a one-off bracket for your motorcycle.
Step 1: Step 1: Take Some Cardboard to Rough Out Your Idea
Make a rough shape of the bracket and cut it out of cardboard. I use several pieces and staple each in position.
Then take a piece of foam and make a 3D sample...it will cut easily with X-Acto knives. You can drill and tap foam prototype to actually hang everything as it will be.