I have fixed broken grille pieces before. What I do is use a die grinder to cut out the damaged piece and the new piece. After you have your new piece cut out, get the new piece to fit good. Once you are happy with how it fits in your grille, take it back out and sand/file the edges down (were it will be attached to the grille). Then place it back in the grille and use epoxy to bond it in place (I use JB Weld). After the epoxy is dry sand it smooth.
