I think that no exists a specific book for this exam... you must study by varios books and articles.
You can use the older book (for 310-051 exam) to get the principles of architecture, but you must study the new technologies such as EJB 3, WebServices, Sun J2EE Design Patterns and so on in another fonts.
Rodrigo Lopes Ferreira
Sun Certified Enterprise Architect for the Java Platform, Enterprise Edition 5
Sun Certified Business Component Developer for the Java Platform, Enterprise Edition 5 (91%)
Sun Certified Web Component Developer for the Java Platform, Enterprise Edition 5 (82%)
Sun Certified Programmer for the Java 2 Platform, Standard Edition 5 (90%)
Tecnólogo em Informática com Ênfase em Gestão de Negócios - FATEC - Mococa - SP - Brazil
I think the point here is that if you wait around for books you're always going to be behind the curve to some extent. In many ways not having an exam guide will serve you better, as sooner or later you're going to have to carry out your own research in order to make your own decisions.
There is only one book for SCEA-5 by Mark Cade & Humphry Sheil, listed at InformIT and Amazon. Its a sleek guide and may not be sufficient in itself to pass the exams, but would be a good place to start and to know what you need to study and prepare.