Are you after one as you've killed the phillips imprint in the plastic????
If the body of the screw is still intact, drill a small hole down the centre, put a dab of silicone/liquid nails on a small self-tapping screw or similar, then screw it in to the plastic screw. Once the adhesive has gone of it's better than new with a metal head!
I've had to do this on a couple where the end gets mangled by accidental over tightning.