Radio Shack at one time carried a conductive adhesive that contained silver, air drying. I've used it to repair the resistive traces on surface screened window defroster years ago. If they have it still it might work! Auto parts stores used to cary a repair kit for these screened on traces and that product might work to cement the metallic contact back to the window. Or you might have some luck doing a Web search for condustive epoxy or something like that. Good Luck