Before I transitioned, I used to carry my stuff around in a camera bag. It was really roomy and didn't carry any of the social stigma messenger bags had at the time.
(and not having to deal with that social stigma anymore was a nice benefit of transitioning...)
I wear a jacket with big inside pockets. Works like a charm, frees up pocket space in the pants and I get to carry everything. Been doing that for years now. Way-too-big phones became uncomfortable when sitting in a car or other tight spaces a long time ago.
Well I grew up in a dry place that gets 42+ degrees celsius (over 108°F) so I absolutely don't mind wearing a light denim jacket in summer where I live now, where temperature barely reaches 30° C (86° F).
Cargo shorts can also be an alternative, though I understand in some contexts they might not be appropriate aparel.
(and not having to deal with that social stigma anymore was a nice benefit of transitioning...)