Originally Posted by Hendo252

I've had good luck with the "Third Eye" products -- I have had one of their "foam helmet" mirrors on the last couple of helmets and have had no problems.
http://www.amazon.com/THIRDEYE-Clip-.../dp/B000BQXXLQ

I did take off the velcro that they provide and just glue the mount to the helmet with GE Silicone; it fills the gaps and holds firm, but can be removed if desired.

Your mileage may vary but I've been very pleased.

-Tom in SoCal