I made mine out of index card books, that are perforated. When we get home, I can tear them out to put in scrapbook next to photos. A pen slips under the elastic closure and I added a ribbon or shoestring for a wrist strap.
WOW! Those autograph books look great! I want to make my own books for our next trip too, we have so many of the generic books I thought it was time to try something new. Those are just index card books slipped into a clear cover? Impressive -- what great ideas!