I was wondering if anyone has tried using a thin rubber strip wrapped around the bars under the riser caps. Seems to me maybe it would take up a little of the vibration but not sure. Might have to try it one day.
I found that because I've adjusted it so much that it's become loose .. not at the stem/bar point, but at the actual mirror pivot joint. I was thinking of maybe spraying a bit of degreaser in there to get the opposite effect, maybe it would get stiffer?