I had one of those hinged locker keys where the metal bit slides into it.  The plastic gave up so I made a replacement.  The Key is a H29 but these all have different heads.

It's quite niche but if it helps someone out then great!

I've designed this to be paused before the top is printed so you can place the key in and seal it into the plastic.  There is a square that prints below the main print to support the weight of the key and keep it flat while the print continues..

The 3mf file has the pause in place.

I've printed this in PETG.  I think PLA will probably be too brittle but who knows!

(PS)  I appreciate the security concerns about having my key on display but frankly you'd have to know where I work, get past 3 security doors, and find my locker.  At which point you'd have access to some smelly boots, shower gel, a few energy bars and some assorted crap I haven't thrown away.  Also these locks can be bypassed with little more than willpower and a stiff breeze.