I put a pair of mirrors on my mini.  I think they're branded TEX.
They have a plastic mounting plate with a set screw holding the mirror which comes in from the rear side. Is there a metal alternative to the plastic bases?  I"ve knocked the mirrors off on occasion just by bumping them with my arm or hip.

Or is there a good fix for the plastic?  I was thinking about reinforcing the bit where the set screw contacts with some JB weld and maybe a metal insert buried in there for additional stength.