Whether for outdoor or urban exploration, the Maxpedition Monsoon Gearslinger which is already a classic, should fit the bill and it is available at the Military 1st online store... "Maxpedition Monsoon Gearslinger is a unique single-shoulder bag that packs serious toughness with tactical style.
Featuring a spacious main compartment, dual hydration options, and quick front access, it's built for urban and outdoor missions alike. Designed for comfort with a wide strap and airflow padding, it's tough enough for all-day wear.