They are not too hard to recreate either!
These are thin and "scrapbook" friendly...http://andreawalford.com/stampin-up-tutorial-tuesday-faux-page-pebbles
These are thin as well (minus the magnet on the back)... http://www.deepfriedkudzu.com/2007/06/page-pebble-refrigerator-magnets.html
These are a bit more dimensional (maybe better used on altered projects, as they will not lay very flat on a scrapbook page)... http://mapleandmagnolia.com/2010/11/26/thrifty-gifty-idea/
Here are some of the page pebbles Bethany made from the 2nd tutorial. She used patterned paper, a dictionary, graph paper, sheet music, and old Making Memory's Clear Self Adhesive Page Pebbles (remember those???). When I add them to my project, I will also add some bling around the outside of each one.