I also wanted more page markers than the 2 it came with. So this is what I came up with...
I used a cotton laminate by Amy Butler. The cover is a very simple design, unlined. I just measured from the edge of the front cover around the spine to the edge of the back, then added 7 inches (this left me 3.5 inches for each side to hem and fold to the inside). I also added 1" to the book's height for seam allowance. I sewed the pockets right sides together and then turned them out. Then stitched down the section between the pockets at the top and bottom.
I also cut 2 long thin strips of laminate to use as extra page markers. I glued them in between a folded piece of card stock 1" wide, and slipped it down behind the leather at the spine. I could have attached them directly to the laminate cover, too. But I'm not sure how they will hold up and if they get too frayed looking, I'd like to be able to remove and replace them.
I like it! Now I'm looking around to see what other books might need a pretty cover. :)