Have a pic of what your talking about? All I have ever seen is the hard mounted tour pack bracket and then there is a flat plate that sits on the top of the rack. The tour pack rack fits between the license plate bolts and the rail holes beside the shock mount.
That flat plate has a hole that holds the pole light with a rubber gromet, then the radio box has rubberised stand offs that attach the box to the flat metal plate.
All those parts are available most of the time on Ebay prety cheep.
Jeff "Stinger" Brown
Column: "Stingers Heavy Metal"
Thunder Roads Magazine- OHIO
Staff Photographer, Writer, Reviewer