This is a little pen holder that I made as a project in my engineering class. I made it for my 1.5" target binder; although, it fits to most other binders of the same size that I've tried. After printing the holder a little longer that it was supposed to be, I found that it has this feature where you can push it in an out like a light switch and makes it more convenient to use. (Below is a video to display)

Please try it out and let me know if it does not fit to your binder so I can know if I need to make a second version.

Also I added a Step file for Fusion360

Thanks!

Google Photos link to see the holder's feature