A lot of "street photographers" seem to work this way. There were a lot of rangefinder 35mm cameras made with iris shutters and 35mm focal length that are small and very quiet. I own an Olympus XA that would fit this bill. Has markings for hyperfocal settings, and can't be heard at all unless the area is dead silent to begin with.
Bob Walkden wrote, in part:
A local photojournalist round here called Linda Sole often shoots from the hip with a Leica M6 and 35mm lens. Her work is very good; it has been quite widely published and has won numerous awards. She tries to keep the camera hidden so that her subjects don't know what she's doing.
