I have a soft-shell day pack made by Camelback with a pocket for a water bladder and enough room for the essentials. It weighs almost nothing. It doesn't have much for a hip belt, only a strap with no hip pad but I don't put more than ten pounds or so into it anyway. It has a daisy chain that makes it just about the same as a Kifaru pod for riding piggyback on the back of my main pack (a Longhunter) using their dock & lock straps. When I'm packing in camp, it doubles as an external pocket and I keep small stuff in it that I want easy access to like snacks.
