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.