I've got one of those mirrors that clips to the arm of your glasses, but never really got on with it.
I got one of those. I quite like it, but it did take a while to get used to it. Used it not so much for cars, trucks and busses, as on a Brum commute there is always something right up your arsed and it's best to ride with that assumption anyway. I used it more as a 'other cyclist' warning. Or to check on my kids if they were drafting me.
More useful out here for EV spotting.
They're quite tricky to get the angle right, particularly on drop bars as head angle changes with hand position. Probably better on a bent.