This is my recreation of the festool Bit Cassette BT-IMP Sort 3 / Sort 1 or also known as the festool TwinBOX. I have modified the design to accept 7 bits instead of the original 5.

Print the clip part out of a rigid plastic like PETG
print the core holder part out of preferably a flexible filament like TPU.

TwinBOX BB-MIX: Item number 496936
Bit cassette BT-IMP SORT1: Item number 204381
Bit cassette BT-IMP SORT3: Item number 204383