Hooksey
CRG makes probably the best, CNC machined aluminium, all parts available, either fixed or folding. Very expensive, but they just don't vibrate. Unfortunately they're very small, and with the reach to our handlebars they just give a piddling field of view. I had to stop using mine because I commute in heavy traffic and I really couldn't see what was behind me. I now use a generic Chinese bike-shop rectangularish mirror that vibrates and has to be tightened frequently, but I can see behind me (sometimes). And I haven't found anything better.
Ken