Hail Travelers! Behold this TRULY insane bag.
It can be worn with or without the chain, clipped on to another belt, or over the shoulder. You could even wear the chain as a belt. Lots of D-rings to clip things to. 
6" wide by 7" tall (cinched at it's tightest) and 1.5"-2" deep with plenty of room for all kinds of good stuff.