My Girlfriend has a Pop Socket for which one leg of the cap broke off, resulting in the cap no longer holding on the socket. This basic replacement cap fits the original easily (Diameter: 40mm). I provide the FreeCAD file so you can alter it to your needs, e.g. by engraving stuff onto the face. The 4 pins are a bit difficult to print, I used “make overhang printable” in Cura with a model angel of 80° and it turned out nicely. Printing with support is possible but removal would be a pain in the ***.