If the any of the retaining clips or prongs were broken during the removal of the cover, then apply epoxy to those points of the earbud.

Evenly clamp the earbud using zip ties or whatever methods works best for you, until the epoxy fully cures.

Try to avoid pressing the power button when clamping the earbud together

Make sure that there's an evenly spaced seam around the earbud to ensure the best tactile feel of the button press on the earbud.