I have this mirror if you're interested. It's a spun aluminum cone and is 4" in diameter. It mounts close to the surface though. The black area is steel with a 1" or so mounting/pivot bolt.
No idea what it's from.
Looks like a Raydot's reproduction. I like the way they look with solo sindshield and hard tonneau covers. Full screens, not so much. The cobra one Carey posted will be perfect.