I have a very good external mirror, other than the sloppiness in the mirror head where it is pressed in to the twin post.

Can you tell me how I can fix the sloppiness - of the mirror of course!

Crickhollow.

Using your four fingers and thumb, press the glass firmly. Then you can grab and remove the spring ring that holds the glass into the frame. Once the ring's out, the glass can be removed. Then you can access the ball retainer and make a few careful dinks in it with a prick punch to restore its grab. Reassembly is the reverse of disassembly.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.