Designed from scratch in Fusion 360, but used the design from ARC7217 (https://www.thingiverse.com/thing:2819279) as a starting point.

Slightly longer so that the hole to put the strap in goes outside the Ukulele body (at least it does on mine :) )

The clip is also narrower near the edge so that the clip will stay in place. The narrowest part is 2.25mm, and the widest part is 3mm.

I also made the bottom round, so it will fit my Ukulele more snugly. This will fit a Ukulele with a 60mm diameter hole snugly, but might work for others as well.