Between 3 bath/showers, and 4 vanity sink faucets, there are almost a dozen fixture handles with these decorative & functional (they hide the screw head) index caps/buttons in our very typical home. If one somehow goes missing, replacement is a snap. Be aware--there are many different finishes, so order carefully for an identical match.

Fit perfectly, made it watertight, looks like new.

You can get repair parts if you’re willing to look……