Hi. I'm using a five-year-old Mamas & Papas pushchair (A3 pramette) for my son that I used for my daughter. However, I'm desperate for a missing part and Mamas & Papas can't supply it because the pushchair is too old. The part I need is a 'pin' for one side of the back rest. Without it, only one side stays in place. Does anyone have any suggestions? Thank you!