I ended up going through a variety of Epson people before getting to the right person.
The number is 562-276-1305, although you can also start with 800-234-1445.
The part number has changed from F191110 to F19140.
Changing the head and dampers was pretty straightforward, helped by Eric's great video.
Anyone who can follow directions should be able to replace the print head,
although I found that it took a solid afternoon to do everything.
This might be because I took the slow/deliberate route - it can probably be done in under an hour.
Right after placing the print head order, I noticed that Vistek Canada has the P9000 on for $5,649 CDN.
With the new print head, dampers, and wiper blade coming to $2,400 US (about $3,200 CDN), I think that I actually was silly to replace the print head instead of getting a new P9000 (which would have had better blacks, possibly less of a tendency to clog, and a warranty). Sigh...