On my 09 7.3FX I have mirror similiar to the Third Eye bar end mirror which is nice since it slides inside of the bar then twist to tighten up. It folds out of the way when not needed. Which ever mirror you decide make sure it's glass and not plastic junk. I paid $12 at LBS for mirror.

http://www.amazon.com/Third-Eye-Bar-.../dp/B001600YZ4