If you can't find it online then build it yourself. I was working on a vintage Transformer for a client. The arm had broken off and it seemed impossible to find a replacement pin without sourcing a donar toy which I didn't want to do. As a result, I created my own design and 3D printed a replacement. Not only did this provide the fix I needed and enable me to go back to the client with a functioning toy, but it has taught me some useful skills. The added bonus is that if I ever get a similar project to work on, I have the means to print more if I need to. I plan to create some more designs, offer my skills as a service and I will make the files available online as I create more.
I recently had a remote control K9 from Doctor Who come into the workshop on behalf of a client. There were a number of repairs needed to get this toy fully working again, but also some pieces were missing. One such piece was a corner stud. I designed a new piece in some CAD software and successfully printed a replacement which fits perfectly into the overall toy.