I found these battery holders on Thingiverse. I printed the one to hold AAA batteries a while ago, and printed the AA one last night. The thing on the right is my honeycomb cable holder for USB cables.
I go through a lot of batteries for my Tidepool work, given that I have dozens of glucose meters and insulin pumps that need to be powered. It's nice to have a compact and stackable design to keep them all in one place.
When I eventually start using an different colour filament I can print the lettering that goes on the front. For now, it looks fine even without the different colours.