Hi Douggie . Great intro . I believe the part you are referring to in your slingshots that is broken would be the "kicker arm" . It's an L-shaped bracket that attaches to the coil plunger under the playfield and has a nylon head on the other end to "kick" the rubber / ball out . Most of the commercial guys here stock them but you will have to double check compatability / part # with the one from your game .
Cheers,
     Scott.