The "Nothing ear (open)" is a really nice pair of open earbuds with one flaw: the transparent cover is easily detatchable from the hinge, and hardly reattachable (even with CA glue).

This is a case that keeps the transparent cover on. Due to the symmetry of the device and the tolerances i've designed (see cross section), you can also use the case as a replacement cover itself. It also includes a keychain hole.

You can print it verticially without supports. Note that the base surface area is low for this model, so the bed adhesion will be low.