Loose Mirror Woes

Nothing terribly exciting to report. I have been having some issues with my right side mirror which constantly seems to vibrate loose. I had heard previously that this was a complaint common to these scooters whereby the mirrors have both a tendency to shake loose as well as carry to much vibration to be useful at speeds. I cannot comment on the second however as I have stated I am experiencing the first. I now carry a set of allan wrenches with me just in case this happens which seems to be atleast once a trip. Now keep in mind a good portion of my riding is in the city with its many potholes and bumps which certainly doesn't help. Also I have been careful about screwing the mirror back down as the bolt only goes down into plastic, thus being prone to breaking from overtightening. So I have started out gently screwing it back down and gradually increasing the pressure each time. Well I have it about as hard as I can manage to get it and well atleast after this trip it has stayed. I am not that optomistic however and have a set of lock-washers waiting at home for me to try. I have also heard of people effectively using loc-tite as well as rubber washers to help remedy this problem. I will keep you all posted as to my results.