Got a source with no page numbers? That’s okay. Skip the page number. “(Smith and Johnson).” Poof. Done. Just make sure your reader can find the quote in the source.
What about a source with no authors at all? Use the title in quotes (for an article) or italics (for a book). “According to the article ‘How Cats Became Our Overlords,’ the phenomenon started in 2012.” You’ve survived the wilderness.