Ye olde Sturmey Archer AW. I've got one in my main ride as well as seemingly 85% of bikes built between 1950 and 1973. If you are so inclined you could buy an old 3-speed for pocket change, take out the gearhub, and build it into the wheel. They're indestructible and parts are readily available. IIRC they're also almost exactly the same width as a SS freewheel hub.