Axiom's Columbus DLX Trunk Bag is a great way to carry your stuff. It boasts durable, water-resistant 600-denier polyester fabric, a large insulated interior, shock cords on top to store even more gear and side pockets that open to become panniers. You also get a waterproof rain cover, reflective piping and a shoulder strap.
Volume: 976 cubic inches
Dimensions: 12 x 9 x 5 inches