Once you stop caring about appearances and go mainly for comfort, the "tactical" clothing (of a more lightweight variety, usually marketed as "duty" for security guards etc) becomes a surprisingly good choice. You get durable cotton/polyester or cotton/nylon blends, plenty of pockets that are actually designed to hold useful things in a comfortable way (like a phone pocket that can fit a Nexus 6P), generous cuts that do not constrict your movement or feel tight when you sit down, often with an elastic waistband that's not noticeable on the outside.