I have several T12 tips laying around so I've created case for them. The hinge is fitted with 1.75 filament piece so no screws/metal rods are necessary. The locking mechanism is a little bit larger (the tip of it) so you can cut it down with pliers to fit your preffered stiffness.

Reccomendations: 

• Print in PETG if possible,
• Print only caseBottom_test to test if the sanppiness of the holder is ok for you and the hole in the ginge allows insertion of 1.75 filament piece.