I have a bar end mirror that extends out. It's a regular mirror... not a concave lens and it's fairly good sized. I spend most of my time on the tops of my drop bars and leave my mirror adjusted for that riding position. I started using this mirror a year after starting commuting by bike. I initially used the the "take-a-look" mirror... hated it. I believe the mirror I use is made by blackburn.

https://www.amazon.com/Blackburn-Mul.../dp/B000BNZ0NI

I liked the mirror so much on my commutes that I added one to my road bike. I've been using the mirrors for nearly 10 years now. I couldn't imagine riding now without one, anymore than driving my car without mirrors.