That sux!
The R3R has no hole.
I'd try cleaning the underside of the fender, gluing a thin piece of tin underneath, and then filling with JB Weld.
Touch up paint may finish it off nice.
I assume you are referring to the pillion mounting point toward the rear of the fender. I just have am M6 thumb screw there since I go back-and-forth between dual and solo setup. In your case, you could glue a hula dancer or a bobble head over the hole