I got the part numbers from MD Charlton and had TacOrd order 'em for me. Turnaround was 8 days shipped to my door, but I'm local so expect a few days longer for BC. You need to let MD Charlton know which extractor you have ie long or short.
If you have the newer long extractor, Sig recommends replacing the spiral roll pin with a new one each time it is removed. If you look at it, it's like a double layer roll pin, not your standard type. Might as well replace the double extractor spring while you're at it. Just use a proper punch when removing the roll pin or you might muck it up. It's a half-circle slot for the punch.
If you do have the long extractor, here are your Sig parts below. Contact MD Charlton to verify if they are in stock.
New style extractor: SIGP1201010
Pin for new extractor: SIGP1300234
Outer spring: SIGPSPRING-10
Inner spring: SIGPSPRING-9
In 2014 when I ordered these parts, my total was $55.50 before taxes and shipping from TacOrd. Prices have most likely gone up by now.
Good luck.