I'm a bit of a bag nut and found a new favorite for what you're describing... but it's actually a duffle bag with nice tuck-away backpack straps... kinda like those Northface Cargo duffles with back-pack straps, but a lot nicer. For me, it has just then right mix of lightweight/foldable yet durable/heavy duty fabric, with the serious YKK zippers, and a lifetime guarantee. It folds up into its own pocket, smaller than a cereal box. It's an Osprey Transporter 60L, which is the smallest with backpack straps. All 3 dimensions are about an inch too long for regulation carry-on. But as a soft sided bag, as long you don't stuff it full, it will easily fit to those airport "sizing cages." I like the idea of having it slightly large, in case I buy stuff and wanted to check it. All straps, zippers, handles seem very well protected and covered with no loose dangling straps - a real plus if checked to those ape baggage handlers.