I used the same inexpensive camo backpack that I use while deer hunting; like BillC, I used it as one of my carry-ons as well. In it I carried my camera, bottled water, spare socks, flashlight and headlamp, spare batteries, spare ammo (in addition to what I had on my belt), binoculars, do-rag (for my bald head, if it got too hot), stocking cap (if it got too cold), gloves, and a small first aid kit, and some TP in case nature called.
This is what I took with me in the safari truck.....when we got out to make a stalk, I just took my camera, multitool, binos, and put them in a fanny pack that my wife got me (well, not the binos...they went around my neck).....I was a little skeptical at first, but I think that the little fanny pack was just the ticket for hauling just the right amount of "gear" for a stalk, while I had the other stuff in the truck in case I did need it. The little fanny pack was certainly a boon while climbing around the mountains for kudu, me being a flat lander and all.....................