Ibm 9513-ag1 flat monitor broken switch

I have the same monitor. I had the same problem you have. I couldn't find the correct replacement part so I improvised. The plastic part you refered to just activates a micro switch on the circuit board. In my case the micro switch worked just fine so I used 5 plastic buttons off of some ball point pens as a replacement. I took the monitor out of its plastic case and drilled holes in the front bezel directly over each of the 5 micro switches. I then put the buttons from the ball point pens in holes. So now the push buttons from the ball point pens act as a substitute for the broken part. I hope this helps.