I'm a big fan these days of a small crossbody bag (aka a sling bag). MY problem is that the pockets on my pants are too large and loose and I don't want to worry about things absently falling out when I sit.
Uniqlo makes a solid one for $25. It's light, comfortable, and unobtrusive. Admittedly, it's not ideal for all styles or situations, but I love that it's large enough for items that are definitely too large or uncomfortable for a pocket, like a book, small notebook, or an accessory.
https://www.uniqlo.com/us/en/products/E486766-000/00?colorDi...
I started bringing a crossbody bag and now I find I drag half the house everywhere like one of those every day carry people because why not, it's so easy to carry stuff compared to using pockets. Very useful to have a battery bank and cables with you.