Got a bar end mirror for the '95 sportster project and instead of paying the extra $20 for the mounting adapter I figured I'd spend twice the $$ in time and a little in materials. I may not be smart sometimes, but I did enjoy making it.
-1" solid round aluminum, about an inch or so
-3/8 16 tpi stainless cap head allen bolt
-3/4" rubber well nut, with the shoulder ground off