I just got one of
these from Amazon. I love it. I took my tool belt, removed all the pouches, and clipped this to it with Alice clips. It also came with a shoulder strap. I don't know how many CCs it is, but I have enough room for shells, turkey calls, permit, license, and ID, a knife, and so on. There is a larger version as well but I think you will have to get it from Galaxy Surplus or US Cav.
Amazon has several different butt pack styles, and they all would probably work.