As an example outside rear view mirror glass that comes off sometimes is being attached to metal and sometimes to rubber. It can be repaired with Mister Glue in minutes. As this glue will bond pretty much anything to anything you should be able to use it whether the backing is meta,l rubber or plasticl. You can get replacement mirrors of different sizes at an auto parts store. Cut to size if necessary with a glass cutter to fit exactly. Wipe off any dirt or old glue from both surfaces (the glass and the rubber). Also, if you have to use something to make sure any grease or oils have been removed. Put several small drops of glue on the back of the glass and press the mirror firmly into place. It should adhere within a couple of seconds. Give it a few hours to fully cure. If done correcty it should be a permanent bond.