Once, again the simple solution seems to be the ideal solution. After the Apple 3.5mm headphone adapter, here is the PencilCozy, a rubber attachment that makes sure you do not lose your Apple Pencil cap.
Available in white, teal and the best, glow in the dark, CozyIndustries really nailed it with this little gizmo. If you do not know them, they make similar products for all your other small gear that can easily be lost. Go check ’em out!