http://www.amazon.com/Writings-Knowledge—Philosophical-Chapters-Heresies/dp/1470149249/ref=sr_1_1?ie=UTF8&qid=1434070160&sr=8-1&keywords=The+Fount+of+Knowledge
I know you can buy it on Amazon, you can even download it in places.
But I am not a scholar though, and to get a full understanding of it ...it really needs a through breakdown to get the full ancient context.