I'd try SIG first, and tell them you're an old SIG armorer from the days when your 220 was using that internal extractor.
I only have one old style 220 extractor, which I keep on hand for a close friend who likes to shoot an old-style P220 that uses that early extractor. I picked it up in my SIG pistol armorer class more than 10 years ago, and put it aside against the day he may wear his out. (He likes to shoot virtually everyday on his rural property's range.)
It's probably (I'd think) going to be machined stock. They wouldn't use MIM because MIM doesn't work as a "spring". I remember back in the early late 80's/ early 90's a local sheriff's office temporarily suspended authorization of their deputies to use the older P220's when an extractor broke. As I heard, it had been a problem with how a batch of the older extractors had been heat-treated, and SIG sent them replacement extractors, after which the 220's were again authorized.
In my old Colt pistol armorer class the instructor chuckled and explained how Colt engineers had quickly figured out that MIM doesn't work for the extractor in their Model O pistol, since it doesn't work as a spring.
Make sure you replace the pins, too.
Have you updated all the wire springs, since yours is down for the moment? Might as well.