[bboozzoo]

This looks like a choice is a serious eye injury if you roll is something you're looking for. Why not buy a handlebar mirror like this one https://cateye.com/intl/products/accessories/BM-45/ I have one on each of my bikes, road/gavel/fitness. Dirt cheap, gives very good rear visibility and very compact size.

[SequoiaHope]

Handlebar mirrors won’t give you as much field of view and you can’t steer them with your head.