I know there are other cap extenders online. But they did not fit. So I made a new design providing the
FreeCAD model. With the FreeCAD model you can adapt the model to your specific snapback cap.

I did this design for a friend and added his name in the Prusa Slicer. The 3mf file is in the download section.

I would print in PETG, because it is a little bit more flexible.
If you need help adapting the model to your specific cap size, let me know and I can help you.