Are there any stats for the NX-class ship? And if so, where?
After looking, I didn't find any, but I am sure I've seen them printed somewhere before.
The Command Division sourcebook for Star Trek Adventures is available in PDF format on DriveThruRPG, as well as on Modiphius Entertainment's website in PDF and hardcover formats. The product description mentions that the NX is included:
The Command Division supplement PDF includes:
- [...]
- Over a dozen additional starships and support craft to command and pilot, including the NX, Nebula, Sovereign, and Steamrunner classes, as well as many shuttle types and the indomitable Work Bee!
According to this Reddit post by /u/Takeshi_Yamato on /r/StarTrekAdventures, the stats for the NX-class ship can be found on p. 54 of the Command Division sourcebook. I don't own the book, so I can't confirm this page number myself.
(There also exist homebrew versions of the ship, including one credited to /u/AdmiralTrek in the comments of the Reddit post linked above, and one by "Jester" David Gibson on the Continuing Mission fan site.)
As of August 2020 there is now an official set of stats for the U.S.S. Enterprise NX-01, rather than the NX class in general, in the Star Trek Adventures: Enterprise Player Characters PDF, available from the Modiphius website or DriveThruRPG.
Note that there have been corrections to other parts of the book, so if you acquired the PDF earlier, you may need to update.