inspired by Scott Yu-Jan's idea of using blank hotel cards and Kazik's note system, I decided to design something that was smaller and quicker to print. 

this uses any blank card that fits the ISO standard but I used some blank RFID cards 

it holds about 15 cards (including the slots and the display) and the storage space stores about 10 cards. it'll hold markers up to about 15mm in diameter 

prints in about 2 hours on an ender 3 and uses about 25g of filament 

printed with PLA at 0.28 layer height and 20% infill