Seasoned one-bagger looking messenger style flight bag

Hello one baggers! I've been one-bagging for traveling for quite a few years but I'm now looking for a flight bag (I'm a pilot) and looking for your recommendations. The requirements are:

• Messenger style shoulder bag (NOT a backpack), preferably like a tote style with a zipper across the top as opposed to a traditional messenger bag with the large flap opening

• Sits upright on its own

• Built in organization (not just one large compartment)

• Preferably machine washable

• I think 12-14L would be minimum size

• WELL built (I'd prefer not to have to buy another bag, ever)