I saw a good one at Purchase Officials Supplies.
http://www.purchaseofficials.com/index.html. The one on the website has three man coverage.
I have always used the one that I was given by IAABO when I worked in an IAABO state. It has both two and three person coverage and a list of topics you can discuss for pregame. I usually run through the entire list when working with a new official. With an old one, I like to take one of the special topics and talk about one of the topics. Block/Charge, Illegal Screens, etc.