[Arran]

 The grille was very likely made out of pot metal, sort of an aluminum and zinc alloy, so there would be two approaches to repairing this grille. The first would be to take the pieces to a plating shop, and have them stripped, then copper plated, you could then attempt to solder the pieces back together, but you will need to grind the pot metal back to make room for the solder and or add a strip of copper or brass to hold it together from the back side. The second option would be to make a new grille bar, out of brass, have the rest of the grille stripped, copper plated, and then solder the new bar onto the rest, then copper plated again, then nickel, and then chrome. The third option would be to make a completely new grille out of brass, steel, or what have you, and then have it copper, then nickel, then chrome plated. 
Regards
Arran