vferog55

I was given a Singer Featherweight II Model 117 that the stitch selector knob is broken. The knob will pull completely out. I took the front and back cover off of the machine and found a flat metal piece with a screw hole and a rectangle hole. I also found a little black cog/wheel that fell out. It appears maybe a screw is missing but I have not found one and I'm not sure what size/length of screw is needed. Question is can anyone tell me how the knob and pieces should be assembled. I know this isn't a vintage machine but am hoping someone can answer the question for me. I have the instruction manual but of course it doesn't show how it is assembled.

Thank you advance for any assistance you can give.