Garden stores/sections sell circles of green Velcro you can cut; I figure of it's good enough for UV then it'll work in a box.

As a bonus, you don't need to raid her hairbands.

Bike shops have yards of that stuff in the late winter/early spring. At least Trek shops do, dunno about others. Trek uses it to tie stuff onto the frame in the box to keep it all from rattling around.

Ooooooo...... I hadn't thought of this. Thank you!