Using a zipper to close a bag is as easy as it gets. Since it only comes in black, your colour choice is made very easy.
From Amazon
16" Sagano EcoSmart Campus Backpack - Black/Grey
Technoworld PLC
Targus Sagano notebook case 39.6 cm (15.6") Backpack Black, Grey
This product is also available at 3 unverified merchants.