Space Naught said:
I Might take a stab at this later today (Or enlist one of the engineers at work since they all use milwaukee everything)

Someone remind me in a few days, I suck at coming back to update lol....

Lil edit: I found these models while digging through Thang's search... https://makerworld.com/en/models/993850-m12-battery-packout-holder#profileId-969814 https://makerworld.com/en/models/1105634-m12-battery-packout-holder#profileId-1101456

Might be easy to just R-E some models since im too lazy to model the battery cavity myself

Be sure to check out Thingiverse and Printables. Thingiverse has a LOT of Milwaukee stuff, just the search function isn't all that great. Printables is catching up in content as well.

https://www.thingiverse.com/thing:5028921
https://www.thingiverse.com/thing:2493518
https://www.thingiverse.com/thing:3994613
https://www.thingiverse.com/thing:5229372
https://www.thingiverse.com/thing:1977186
https://www.thingiverse.com/thing:5773246
https://www.thingiverse.com/thing:4003040
https://www.printables.com/model/119513-milwaukee-m12-battery-holder-new-version-5
https://www.printables.com/model/638160-milwaukee-m12-battery-holder
https://www.printables.com/model/459511-milwaukee-m12-battery-holder-for-ikea-skadis
https://www.printables.com/model/1080078-m12-battery-holder-magnetic
https://www.printables.com/model/1262079-milwaukee-m12-battery-holder

Note: these links aren't specific to the Milwaukee Packout, just generic M12 holders.

Packout-specific:
https://www.printables.com/model/1020635-milwuakee-m12-charger-batttery-packout-insert
https://www.thingiverse.com/thing:5783565
https://www.thingiverse.com/thing:5721605

M18 Battery Holders for In-Car Storage

Milwaukee M12 Battery Holders & Packout Inserts

Often appears with