You're not going to find a pattern that will work perfectly, you're going to have to do some altering. I'm going to be making mine using the matrix pattern (works for everything, I'm tellin' you, lol). All I will have to do is:
-take the top backpiece and cut it/tape it to the other back piece
-altering the side front and side back pieces on ONE SIDE to close the arm hole so that you only put the sleeve on one side
-Add a hood
-Shorten the front piece so it doesn't cross all the way over and just leave off the collar
I'd suggest finding someone who can SHOW you how to alter a pattern, cause I can try to explain but if it's you're first time making something you're gonna need some help. While his cloak LOOKS easy, it's not. It's fitted on one sleeve and the torso like a coat/jacket, but has a hood and the arm is closed on the other side like a cloak...so you're not going to find something to match perfectly, you gotta make it yourself.