Side Mirror Repair

Anybody know what would be the best place to get the glass for apassenger side mirror? I don't want to buy a whole mirror assembly, just the glass with the plastic piece on the back to mount into the existing assembly. The stupid mirror assemblies are fixed, so they don't move if bumped and I bumped into it and shattered the glass. I found whole mirror assemblies for $35 or so, but would prefer paying less by only getting what I need. Thanks for your help.

Almost any glass shop can cut you a piece to fit (they even carry convex "items in mirror are closer than they appear" type glass), and you can use double sided tape to stick it to the old piece. You can take a small hammer and carefully break and remove all the old glass from the backing piece if it's too shattered to stick the new glass to.

Problem is, the plastic backing piece is gone (I think at least - I think it fell off while driving, as when I bumped it, it knocked it loose. Have to check, though - I don't have the car with me at the moment).