How can I fix the switch on my Bosch 2200 garden shredder?

I have a Bosch Rapido 2200 shredder. The on/off switch stopped working and I have taken it apart and tested it by depressing the switch manually. The motor runs perfectly well. It seems that the issue is the safety switch that operates only when the screw holding the cover is engaged properly. I can't see any broken plastic components inside and am able to bypass the safety switch by stuffing a piece of rubber in it to keep it permanently depressed. However this is none too safe and I would rather be able to repair it