A Traveler's Notebook isn't disposable, even if it gets beaten up. The leather cover is extremely durable, and the smaller parts are all replaceable with this repair kit. It includes eight colors of elastic, a replacement tin charm, and two replacement bookmark strings. The replacement parts are the same for both Regular and Passport Size notebooks. English and Japanese instructions are included in the package.
Even if your elastic is still holding strong, consider picking up the repair kit so you can customize your notebook with a fresh color or an extra bookmark.