If you want to make your own rock journals, you can print out the cover here. It prints out on 8.5 x11 inch paper and then you fold in half for the front and back. I found it works best on card stock, but any paper would work, so don't let that stop you! Then add as many interior pages as you want, I used two pieces of paper per journal, which was 4 pages. I didn't want too many pages to make it overwhelming for my girls.
To hold the pages together I used embroidery thread. I used one continuous thread, sewing through the top, then through the bottom. I left the ends on the outside of the journal, so I could tie them together. (You could also staple!)