An inexpensive, very functional, very discreet solution for me is a messenger style school bag with a good shoulder strap. My lenses live in neoprene lens socks as does my flash, my external power supply and a camera body. This does not scream "expensive stuff inside", molds nicely around the hip and access to gear is quick and easy. School bags of this type can be had with a multitude of "cool" graphics on them, if that is what you want. Neoprene lens socks are in the $20 dollar range from camera suppliers or can be made just as well for about $1.00 worth of neoprene and 10 minutes on a sewing machine.