One of my many hobbies is lockpicking for sport and fun, and I really like the brass practice locks from Sparrow (no affiliation). They're not too bad to pick in-hand but my weak hands still cramped up from holding them after a while so I modeled this grip to make it more comfortable and keep my tools handy.
I also added a barrel key holder under the lock — it won't fit standard keys after repining, but it's perfect for the keys that come with the progressive and cutaway locks.

I printed with 0.4mm nozzle, 0.2mm layer height, oriented standing up with no support and 7% gyroid infill and it came out great, it's a very easy model to print.
As always the tolerances will depend on your printer, calibration, slicer settings, and filament, so you may need to rescale to compensate and get a good fit. It should be tight enough to hold the lock without rattling, but still be loose enough to slip out without needing the key to pull it out. At 100% scale that's what I get on my Ender 3 v2 and Bambu X1C.

If you're left-handed or find the angle uncomfortable, try out the mirrored version!

With the progressive lock set and some repining I've kept myself occupied for ages and this just makes it a bit more comfortable so I wanted to share the model.

Happy picking ✌