Recommended translation: "Sophist" in The Being of the Beautiful: Plato's Theaetetus, Sophist, and Statesman,  trans. Seth Benardete (University of Chicago Press: 1984).

About the dialogue:

In the Sophist, which takes place the day after the Theaetetus and was written c. 360 BCE, Plato explores what constitutes sophistry and how sophists differ from philosophers and statesmen.

Online:
Amazon (Recommended Translation)
Project Perseus (English, Free Access)
Project Perseus (Greek, Free Access)
Project Gutenberg (English, Free Access)