After a little bit of research and brainstorming, I thought of a possible solution. Many of the students have grown up using technology on a regular basis. Why not show them how to use technology to accomplish the goals of commonplace books, especially when they are more comfortable with this format than the traditional pen-and-paper writing? Blogs are (or at least can be) today's commonplace books. Blogs can not only help students keep a written record of their learning, but also add to the variety of formats they can use for self-expression.
I'm excited to tell them about the different format and have them test it out for themselves!