You'll most likely want a mix of files for your exact needs.
If you're using a 48-22-8436 5-Compartment Low-Profile Compact Packout, you can fix 3× Slim Long Bit Bins (or a mix of half-width bins)
If you're using a larger 48-22-8431 11-Compartment Packout case, you can fit 6× Slim Long Bit Bins and 5 Low-Profile Middle Bins (or a mix of half-width bins)
More details and design files here:
https://3dprints.electronsmith.com/slim-packout-bins-milwaukee-bit-holders/
https://3dprints.electronsmith.com/milwaukee-low-profile-packout-middle-bins/
https://3dprints.electronsmith.com/milwaukee-tool-style-bit-holders-v6/
Polymaker Matte PLA Filament 1.75mm Army Red is a good color match
Once you're done, make a label for your slim packout with this: https://www.printables.com/model/408222-low-profile-milwaukee-packout-handle-labels
Also contains files from:
Update 2/2024: I've found that some of these have loosened over time and don't hold onto the bits as well. I re-exported them from OpenSCAD adjusting the spring thickness to .4 and they work much better. Use the Milwaukee-case-bit-holders-V6_0.scad file
The author remixed this model.
Edits to sizing