A caulk tube cover or plug.

Found on thingiverse but the stl by itself was certainly not convenient to print.

Found ideal settings including brim, raft, and supports. Sharing so you can skip the effort of the same.

Note, the support gap is very small in my profile. This was necessary for it not to move around while printing. For my P1S, the support still came off beautifully but if your flow is different it might stick too much. If you find supports don't remove easily, try increasing the top layer support gap.