I like the Diamond Ball bag. I used to have a black one, and it was great. The internal pockets are well-sized to keep organized an indicator, brush, and pen. The internal pocket depth is such that accessing items is easy without the items getting caught.
The grey ones, however, use a fabric that is not even close to matching a standard heather grey umpire slacks. The stitching on the bag contrasts instead of blends in.