It looks to me like the pockets are just on the bottom, like the envelope it is supposed to be, and not all the way around. It should be easy enough to duplicate without a pattern by just adding wide diagonal flanges of folded fabric to the lower corners before you sew the bottom and side seams.
Or you could try contacting Connecting Threads to see if they would consider adding the pattern to their free pattern collection online. Couldn't hurt to ask.