I'm very sorry that breakage occured. All of us I 'm sure, would hate to loose a numbered part of a nice gun. I hope Lugerdoc can help you out. He does have many numbered original parts and who knows, you ,might be lucky.
There's a good chance that the part may have been damaged sometime in the past and the breakage was just bound to occur. Things do break. But, when the new part arrives make sure the bearing block and recess for the extractor spring are cleaned out. Powder build-up under the extractor or jamming the performance of the extractor spring could lead to another breakage. I've only owned a few Lugers in my day and every one of them had rock-hard powder under the extractor and so much in the spring that it could barely function when I got them. I'm writing this as a reminder to everyone who shoots Lugers too, not just you. Good luck and Happy Fourth!
Dave