Hi, Katherine! Welcome to the Disney Parks Moms Panel.
I did a little research on this for you, and I think the Bitbelt Jr. should fit around a
MagicBand. I measured both a MagicBand and a MagicBand2, and the width of the lower portion of the band (where the holes are) is the same for both (whether or not the grey outer portion of the band is removed). The only discrepancy is at the top of the band. On a regular-sized MagicBand, the upper portion of the band is ⅞" wide, whereas it's only ¾” wide if the grey outer portion has been removed. If you're looking to use the Bitbelt Jr. on a regular-sized MagicBand it might be a tight fit, but it should work.
I've been using MagicBands for my Walt Disney World Resort vacations for the past 3.5 years, and I've never had one pop off my wrist. (My husband and 9-year-old daughter have never had a problem with theirs, either.) If you're concerned, though, about the possibility of losing a MagicBand, I would recommend looking into purchasing a
Mickey Mouse MagicKeepers Lanyard Medal or
Disney Parks MagicKeepers Carabiner. Either of these will allow you to pop the Icon from your MagicBand2 into the MagicKeeper and then clip it onto your lanyard, bag or belt loop. They're a great alternative for little ones who may be tempted to play with their MagicBands, too!
Should you misplace your MagicBand during your Walt Disney World Resort vacation, simply visit the nearest
Guest Relations location to ask for help.
I hope this answers your question, Katherine! Have a magical day!
Amy