I should add that in the old days I used a SeeBak mirror, which was "mounted" on the back of your hand, held in place by an elastic strap. It was quite big and gave a really good view. There's a NOS one on the bay now. https://www.ebay.com/itm/13563981485...mis&media=COPY

I used it for years but my salty sweat eventually worked through the paint on the mirror's metal backing. The mirror fell out and broke, dammit.