Broken plastic clips on bullet mirror covers is a common problem and when it happens the covers work loose and need to be fixed or replaced.
If you have powerfold mirrors I know from experience that it is essential to have correct fitting covers otherwise loose ones can stop the mirror movement, jam the mirror and damage the motor gears.
If the exterior of the covers are fine and in good condition it is a waste to just discard them.
One option is to buy new ones if and when you can find them, and if you have the chrome type a pair of new ones can cost around £60 on E Bay
You can always try and glue them in place, which may work but is not always successful.
So I have come up with a fix which should be permanent and at less than £5 is both cheap and easy to carry out.
The covers can also easily be removed should the need arise as when the screws are undone the covers will pop off
Robs Car Gallery
click below to access nano website
Planning is an unnatural process, much better to just get on with things, that way failure comes as a complete surprise instead of being preceeded by a period of worry and doubt