Via the Japanese Amazon website I found a diagram of a crane box. Some of the books on Amazone websites have a few pages you can view. If you look for the book with ISBN483472607X you can look inside and find the diagram.
I also have a Dutch origami book in which a diagram is included for an envelope of crane (one piece of paper). In Tomoko Fuse’s book “Home Decorating with Origami” are instructions to fold another crane envelope, but this is made out of two pieces of paper.