During a stay in Sifnos, Greece last summer, I discovered the tourvas. An everyday staple for most working class Greeks, tourvas bags are used to carry the essentials and the extras. In keeping with the bag's minimalist design, there are no unnecessary zippers or buttons: instead, it's closed using drawstring straps which are tied around the top to keep all contents exactly where they should be. Here's how it's done:
Tourvas bags are available at Loti Market.