I have full length back pockets in three of my binders – my pocket and A5 Mia Caras and my personal Compagna – all by Gillio.
A full length wallet pocket across the back of a binder is a fabulous feature and once you get used to using a binder with it, it is something you really miss when you use one without it. It can be used to store A4 papers (in the A5) and larger pieces of paper than a binder of the size can usually store. In the pocket sizes it can be use to store notes (as in money), making it more functional as a wallet.
Full length wallet pockets on binders are more widely available in pocket and mini sizes – find a comprehensive list of these at Philofaxy.com
Below are some brands with the harder to find personal and A5 sizes featuring a full length back pocket. Raika is available in personal size only. ,