Inspired by LoboCNC's (https://www.thingiverse.com/LoboCNC) print in place capo design. His uses a rubber strip in the presser bar (https://www.thingiverse.com/thing:988513).
I decided to make my own design as part of a scholarship application for 3DHubs. This version is still print in place but requires one rubber band instead of a rubber strip (no clue where to get one of those). Designed to use a generic tan-colored rubber band about 6cm in diameter or 2.5in.
NOTICE The clamping force on this capo is not as strong as a real capo with a spring so keep that in mind when you print it. Works great on my electric guitar because the strings are looser but not at all on the acoustic. (If you are looking for one for an acoustic guitar you may be out of luck as I see many issues in the comments section of LoboCNC's thing.)
Rubber band goes for the loop near the clamp, along the presser bar and up to the horn on top. Pictures soon to follow once I can print this newest version. :)