Remixed Magic Band 2 Strap Keeper by DuaneL and increased the inner width by 0.5mm and inner length by 1.0mm.

The special edition MagicBand+ bands I have are slightly thicker than my older MagicBand2 straps. The increased sizes also factors in printing using PETG instead of TPU (TPU is more flexible).

The strap keeper is designed for the adult strap sizes and not tested with the kids size.

Pictured strap keeper printed with 4.0mm nozzle, 2.0mm layer height, clear PETG.