Greetings. The Para forum is like CTD's marketing department after the election.

I have a Para P10-9, the subcompact double stack 9mm and the ejector broke. Will a single stack 9mm ejector fit and operate? And will any series 80 (this one has a firing pin block i think) 9mm ejector fit in this well enough to get running?

Ejector size is the same across the board for all 1911 and 2011 type pistols (caliber specific to ejector cut on the slide).
Many quality ejectors (Billet/Forged) will typically be oversized or gunsmith fit and will need to be properly fitted...

For example: 9mm/38 Super/40 SW/10mm calibers will generally use the same ejector type, while .45 ACP based rounds
will use one that is caliber specific for the .45 ACP caliber rounds like: .45 ACP, 45 Super, and 460 Roland...

Buying a high quality ejector that is extended (regardless of caliber) makes sense in many ways, I did this every time I
purchased a 1911 based pistol to help prevent "brass in the face" ejection of the brass cases during firing...I took my
time removing the original ejector and fitting a new extended billet ejector (EGW makes really good ones).

Some high quality 1911's come with extended and fitted ejectors as factory standard Item with their 1911 pistols.  

BTW, shorter 1911 slides like for the Colt Commander, Officers sized models will require a longer/extended ejector
for proper function/ejection/timing.

Good luck.

Different cuts to the ejector face...
Link

9mm vs. .45 ejectors types
Link

I should have done a bit more research, I found that out shortly after I made the post.