Not 100% sure this counts as a functional print, since I purchased acrylic mirrors for this and cut them down. What I 3d printed were the templates for cutting the mirrors and the shell for holding it all together in the right shape and protecting it so my niece can play with it without breaking it.

Mirror templates: https://imgur.com/gallery/gKkYyYE

Images through the kaleidoscope, along with an external view of it: https://imgur.com/gallery/P4atHey