+1 on Cal.BAR's suggestion to plug into Calguns. When I was still in So Cal, that was a daily hangout. As to acquiring a 1919, there are always finished guns around, but you may want to consider buying a kit and building one, even though you have to paper everything in CA with the new legislation. Or so I understand. Either way, you won't regret adding a belt fed to your hardware collection!
And I also recommend the m1919tech site for a great amount of detail on development of the Browning.
And I also recommend the m1919tech site for a great amount of detail on development of the Browning.