UNSC Canvas Messenger Bag
From Halopedia, the Halo wiki
The UNSC Canvas Messenger Bag was a limited-production bag sold by Bungie. It was sold in the Penny Arcade Expo (PAX) 2007 and later made available from the Bungie Store. It was removed from Bungie Store's catalog by early 2008.
Made out of canvas, the UNSC messenger bag has two main pockets, with a flap that goes over the outside of both. The flap has a distressed UNSC logo on it along with the following sewn on a patch:
The bag is about 14 inches high and 10 inches wide. It is roughly three inches in depth, while empty.