Have you tried the second hand boating store in Steveston or possibly one of the comercial shops there.
Another, possiblity is to make a sand/clay mold. I remeber doing that in metal work class for aluminum (sp) casting. If your going to try it I would take out a book or too on it but the basic idea is you make two square boxes and put a mold (another ball should do) pore sand in pack it down with two holes on one side to put the lead in and let air out. It should work for lead as it melt at a much lower temperature than Alumimum. Before you try the first time, I would make the mold a few practice times because its hard to make a good mold the first time. Back in the day we make sword, book end, and axe heads this way... teacher thought it was ok to make wepons at school cause alumimiun doesn't hold a good edge.
Have fun, Jason