Warrior Cargo Pack or any of the clones of the MAP pack are excellent for all sizes and regs:
http://www.warriorassaultsystems.com/elite-ops-range/bags/cargo-bag/
Would not buy a molle-attaching pack unless you have a small/medium sized bottle or use a well balanced plate carrier with a lot of magazines on the front. Bottles are heavy and will pull it backwards over an hour or so regardless of how well you have it fitted, and if you just use a chest rig then it likely won't happen. If you're not sure then go for a backpack of some sort. For a 48ci 3000 you'll probably be fine with some molle pocket/attachment/backpack.