Reddit mentions of Third Eye Pro Helmet Bicycle Mirror

I use a Third Eye Pro and I love it. (Although the tape that it came with was too weak -- I had to augment with double-sided foam tape.) It's no substitute for turning around, of course, but for just keeping an eye on things it really makes me feel safer. I find that I can get a much better sense of my surroundings with the mirror, without having to twist around and take my eyes off the road ahead. It's also useful when riding in a group, for seeing if the people behind you are getting dropped. I've gotten so used to it that I sometimes find myself glancing up where the mirror should be even when I'm not wearing it, because I want to know what's happening behind me without turning to stare.

I'm sure there are good alternatives, but I've had great experiences with these. Small, stable, and fairly durable.

You're looking at some attachment like these guys:

https://www.amazon.com/Safe-Bicycle-Helmet-Mirror-EVT/dp/B003LVHZ4O/ref=pd_lpo_vtph_468_bs_tr_t_1

https://www.amazon.com/Third-Eye-Helmet-Bicycle-Mirror/dp/B0015ZZBM6

That's all I can think of, props for figuring it all out and getting the blades on!

Not necessarily a recommendation, but this one works for me, YMMV
https://smile.amazon.com/gp/aw/d/B07MFD8QF3?psc=1&ref=ppx_pop_mob_b_asin_title

I loved this one when I wore a bike helmet. Found hi-temp hot melt glue worked best to hold it in place.
https://smile.amazon.com/Third-Eye-Helmet-Bicycle-Mirror/dp/B0015ZZBM6/ref=mp_s_a_1_6?keywords=third+eye+mirror+bike&qid=1568821343&s=gateway&sprefix=third+ey&sr=8-6