I don't need no convex mirror. I've been using these BIG scooter mirrors for 10 years. They have 50 kinds at BikeINN in Spain.
Slow delivery but good service. I'm looking in them LOTS watching hundreds of truck coming from behind on 90 mile highway rides.
But the problem is I had to make several mounts before I finally found a more unbreakable way.
But then the mirror post has a stupidly short 5/8" thread needing a half inch nylock nut. I needed 1" with a half inch thick mount made from a briffter.
I had to JB weld a bolt in this sleeve threaded and tapped 10 mm.