This is a bag I found at Cabela's that matches up really well against the Grip Eq bag but for $100 less. Some key points are that the upper section and the disc poscket are separated by zipper flap. I heard alot of complaints from the Grip users that they have to pile their stuff right on top of the discs. Also there is sweet insulated drink sleeve and an umbrella holder (really a fishing rod holder). The only things I added were two safety pins on the front pocket to limit how far the zippers open.
Cabela's XPG Pro Series Angler Pack
If you need a larger one check out the XPG Deluxe Angler Pack