Look locale to the lead extrusion industry. The same people that extrude lead for leaded window frames do core wire. These presses are vary large and are usually made in house. It's kinda of fun to watch the squirt process.
In Glendale, Az, I would try and locate Condor metals. They were the top suppliers for rolls of lead core wire. I don't know if they are still in business any more, but they did run two press about the size of fire engines.