For years I've used one of the teardrop-shaped bags from Ameribag. It looks/acts like a shoulder bag, so I've been allowed to take it into museums when smaller backpacks have to be checked. I've never been asked to check it at a museum. The medium size easily holds a wallet, camera, sunscreen, rolled up hat, water bottle, guidebook, maps, snacks, phone, and the miscellaneous stuff I usually carry in a purse. I initially bought it for the ergonomics because I have a repetitive-use injury in my arms and shoulders, and I'm amazed at how much I can carry in it with no pain. It comes in a variety of materials; I use the microfiber, which is the lightest. It also has great internal pockets/clips so everything doesn't get lost in a jumble. And the zipper is next to your body, which is nice for security.