Mikul, I highly recommend the Eagle Industries Liqua-Pak III. Very comfortable. Cargo capacity is about 1000 cubic inches with lots of straps and attachment points. Very comfortable and well made. They are made in various colors. I have a tan colored one that I use in the southwest desert. I carry two hydration reservoirs in it and just keep on moving.
Check out
www.eagleindustries.com and
www.lightfighter.com