Jeese,
I use a camera bag. Small, light, portable, inexpensive. Comes in a variety of sizes. Can be securely attached to yourself or your luggage. It’s padded to protect from impact. Since it’s waterproof from the outside, i presume it’s leakproof from the inside. Should go a long way toward preventing the kind of public disaster YOU got to read this!!!! My little ramble... that Msselva describes. In a major city, i would be very surprised if they did not call out at least the hazardous material units.
Jo Public assumes she knows whats in the bag so it’s discreet. I you wanted be really covert, you could get a bag big enough to actually carry a camera.