RE: Have you tried to make your own bookmark?
I did as a kid--I just took construction paper and markers, decorated a strip of paper myself, and then covered the whole thing with contact paper to make it more durable. You could also give him stickers, or let him cut out pictures from magazines and glue them onto construction paper or card stock. Once it is covered in contact paper, he can even punch a hole in the bottom and tie on a string to dangle a charm or beads that will hang out the bottom of the book, or he can cut a "fringe" onto the top or bottom of the bookmark.
If he likes comics, he can cut out a strip from the newspaper and mount it onto construction paper or card stock and then cover with contact paper.
Hallie
DS #1 5/02
DS #2 1/05
DD 8/09