Bulbs are not available for sealed beam headlamps. If it is a sealed beam, the entire thing is the bulb.
They may be available through Kantner. I may have one, if I do I'll send you a PM. Posted using the Full Custom H.A.M.B. App!
There is a tech here on the HAMB to cut a dead sealed beam and adapt it to a modern style halogen housing. If you have an old one you can trim off the lense and glue it to a new housing. I am not describing it as eloquently as I would like. Check out the tech: http://www.jalopyjournal.com/forum/threads/cutting-a-round-sealed-beam-headlight.580371/