A 10-Year Battery for AirTag

It's a good design, IME. Lowepro makes a variety of similar ones. (I had a one similar to the photo, fitting 2 bodies, wide L, long L, f/1.4 prime, strobes and triggers, and boxes of strobe batteries.)

Lowepro also has day/overnight/carryon backpacks, so you can carry some DSLR gear, laptop, change of clothes, and toiletries, all in one bag.

I still have one LowePro day backpack that I repurposed as engineer/startup briefcase. It fits a huge laptop and misc. stuff for working late hours, and has a DSLR door in the side, so you can slide one shoulder strap off off long enough swing it forward like a sling bag, for quick access to a good camera for serendipitous shots.

Regarding real sling bags, I personally wouldn't use for lengthy carrying of heavy stuff, since it's asymmetric left/right. I even got rid of my grocery canvas tote bags, and use an old backpack for carrying home groceries.