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.

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