Aer makes bags for people who have tried everything else. The Day Pack 3 is 24 litres of considered layout: a clamshell main compartment that opens fully flat, a padded 16-inch laptop sleeve, a quick-access front pocket with internal organisation, and a magnetic water bottle pocket on the side.
The materials are 1680D Cordura ballistic nylon. The zips are YKK 10. Nothing flexes or creaks. At 1.1kg empty, it carries a full day of gear without adding much itself. Subtle enough for an office, capable enough for a weekend away.