Advise your friend that the method of securing bar-end mirrors can be greatly improved by fitting a proper anchor bolt, (aka "Rawlbolt"). I found it necessary to open up the manufacturer's bolt hole a little with a drill bit to take the new bolt. The original mounting mechanism is distinctly Michael Mouse, and the mirror is now solidly secured and pretty much blur free. Highly recommended.
I've tried to attach an image (JPEG file) of an anchor bolt but haven't yet figured out how to - most odd...