I answered this question in the body of the post already, but for the sake of clarity: while the original in-universe book by Newt Scamander, Fantastic Beasts and Where to Find Them (a 2001 charity publication), has an audiobook, theFantastic Beasts movie screenplays, Fantastic Beasts and Where to Find Them: The Original Screenplay, Fantastic Beasts: The Crimes of Grindelwald: The Original Screenplay, and Fantastic Beasts: The Secrets of Dumbledore: The Original Screenplay, are published as books in their own right, and may or may not have official audiobooks, depending on your region and the online stores you use.
This is why I try to stick to a few platforms for purchasing audiobooks, like Audible, Apple Books, and Google Play Books. For the ‘Fantastic Beasts’ textbook (published as a charity edition in 2001), I’m able to find the audiobook for purchase through these platforms, but for the movie screenplays of the ‘Fantastic Beasts’ movies, published as Fantastic Beasts and Where to Find Them: The Original Screenplay, Fantastic Beasts: The Crimes of Grindelwald: The Original Screenplay, and Fantastic Beasts: The Secrets of Dumbledore (The Original Screenplay), I can only find the e-book versions of the screenplays, sometimes narrated, sometimes not.
So long as you state the title, that you are looking for it in a specific country, and what listening device you are looking for it on (such as Audible, Apple Books, Google Play Books, etc), you can search on the respective website for the audiobook. You can also try searching for the specific title in secondhand book stores to see if they have any copies of the audiobook on CD. In some cases, publishers will release the text as a text-to-speech audiobook. Other times the publisher will dramatize the story and include an abridged version of the text as well. This should be noted in the run time and by the narrator’s name in the title of the audiobook. Ultimately, I had to use a mix of the two (ebook and audiobook) for the series, but I managed to complete them all while on the long commute to work, and coziest of reading nooks.