I have something like that in a painted speedo holder from my modern Suzuki GZ250 that I took to the chrome shop -ruberized part I mean-
It was a bracket to hold the speedo lights cables, so I guessed the rubber was there to avoid the cables being damaged with the vibration.
I just shrouded the bracket with heat shrinking tube and shot the heat gun. Didn't care much about originality in a place hardly seen.
Just my .02