This stylish bag pattern from Pink Sand Beach Designs is convertible from a shoulder bag to a backpack.  The bag finishes at 12" wide, 11 1/2" tall and 5" deep.  Roomy with lots of pocket,  4 inside and a zippered one on the back.  Malibu Sling Hardware kit in Silver-Nickel available to purchase separately.

PSB136 - Malibu Sling Pattern