The baseball bat I played little league with 30+ years ago, YEARS of use and misuse and being thrown at games.  The End cap was already half broken, and finally broke and popped all the way out.

I recreated the end cap as close to the original design as possible.  Not sure how it will hold up to extended use in the bat, but it seems to have worked.

Printed in PLA, because that's what was already in the printer.  Could be printed in PETG or ABS for more strength, but I am unaware to how the end cap functions, if at all, other than to plug the end of the bat.  Maybe different matterials would yield different results in how the bat performs, but I have no idea.

Good luck!