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.
It's not cool and many people prefer to be like everyone rather than using what's convenient for them.
For example using short dress for men probably is more convenient as it allows better cooling for their genitalia which is important for reproductive function and generally for health. Yet outside of Scotland dresses are not considered an appropriate for men and nobody even dares to use them.
A good kilt is heavy and warm and if you wear one to a social gathering, it's a hot thing to wear. But wearing it outside is a brave thing to do, particularly in the damp cold air of autumn/winter.
Probably why they have long socks/hose to stop your legs freezing.
I am not brave enough to try it. I am not sure where you are but the UK has a lot of moisture in the air so low temperatures feel a lot colder than equivalent temperatures elsewhere in the world.
eg. a 5°C day will feel a lot colder here than Iceland.
People usually think 80s/90s fanny packs, which look dorky.
Now you have lunatics who feel the need to walk around with loaded pistols, but don't want to have a holster to effectively use it. So you see gun fanny packs in some places.
Looking like a dork or a nut isn't appealing to everyone.
https://images.app.goo.gl/dWdwN4K1uwNe8DGX6