How can I adjust the side mirror?

[DandyDon]

M22 Mike restored my 69 Z28 about 9 or 10 years ago.At the time we used Trim Parts side mirror. The quality was/is first class.The only problem that has developed is the mirror is now "loose"---it won't hold its position and road vibration causes it to point down.I readjust it and in a few moments it's down again.

Is there a way to increase the "friction" so the mirror stops sagging?

There is no screw adjustment---just a ball/socket type arrangement.

Thanks-DandyDon