Standard size ball marker. Dimples in ring allow the ball to be turned making a straight line anywhere on the ball. Printed in PETG but any will work. Slightly flexible to allow ball insertion, and slightly snug to hold ball so you don't get sharpie color on your hands. :) Also used support for the section under the sharpie portion.

If you use some of the oversize balls you can stretch in the Prusa Slicer. The 3MF file may or may not work in your printer, I do some funny things, like commented out the Printer current codes at the end of the Start Gcode. Seems that was causing a lot of extruder movements stopping and restarting, causing skipping or No filament feeding.

UPDATE: Enlarged dimple to hold golf ball more secure.  SharpieBallMarker2 has the bigger dimple.