Philip,
I have Magical Racing mirror inserts on my Bird and can highly recommend them. Not only do they simply stick right on top of the existing glass (thus solving your problem of "replacing" the glass portion only, they also have a convex-like surface that increases the view of both mirrors very nicely.
The quality is top-notch, so no worries there. They don't seem to be available via their english language website anymore (seems like they may be being distributed by a Moto-works.jp named site now.) Though I did still se that they were available through the Japanese site. I attached the url for the Japanese site and hopefully it might help a bit. The Moto-Works site FAQ's said that thing on the Japanese site may still be available, though you may have to call/contact them directly.
http://www.magicalracing.co.jp/LineUp/97_03cbr1000xx.htmlAlso, the price is only $57 give or take with shipping - not bad!
Hope it helps.
Cheers,
Kevin