Do you have much experience with multirotors? It's fairly simple to get a decent rig that can carry a GoPro for 10 minutes (per battery) that weights under 3 pounds and isn't going to be very audible once it's 10 meters or so away. It certainly won't be <2" in diameter, and it won't literally be silent, but it's not going to be the massive disturbance people in this thread seem to expect.