My wife gave me a couple of her pin backed buttons that lost their pins and asked me to 3D print something like a key ring. Putting off what could have been done quickly for a year or two, I finally came up with a design in time for a Christmas stocking stuffer.
The 3D printed ring fits around a small button, holding the button in a groove. The keyring closes the design and helps hold the button in place.
I put one of my oldest buttons, from fifth grade, in one to use as an inner zipper pull on my laptop bag.
You can download the STL or remix the design on Tinkercad. It is a great way to protect but display a cherished button or to resurrect a broken button!