I've got a fanny pack and a large day-pack (2700 cu), both by Bruzer Gear, that work great for me. Never have had to take them off due to thick brush... but I haven't had to walk through lots of brambles, either.
The CatQuiver works very well, too. I have a CQ 4, and I have no complaints. I also have 2 great packs by Summit Equipment... they are heavy belts that suspend a medium-size bag (like a cargo pocket) on each leg, hanging from the belt and securing to the leg. This works well, too, but I've never gone through heavy brush with either one. You'd have to find one of these second-hand, as they aren't being sold new anymore. PM me if you want more info on these.
Lots of good bags out there. Seems like a center-of-the-back fanny or backpack would work best for what you need.