I have three bikes - a mountain bike and a two road bikes. My main road bike has bar-end shifters, so that kind of limits my choice in bar-mounted mirrors. I bought a Take-A-Look mirror, and originally mounted it to the visor of my mountain bike helmet. I was unable to get it adjusted to geve me a comfortable view. I then tried mounting it on my glasses, and find that it works great there.
+1 for the Take-A-Look.