Lay open a real wallet; trace around onto two pieces of medium card stock; cut out. With craft glue, affix pieces back to back.
For pocket, trace closed wallet onto wrapping paper. Cut out, and trim off top half. Glue to paper billfold at edges. Topstitch around billfold and side and bottom of pocket with a sewing machine, leaving 1/4-inch seam allowance.
Wrap elastic ribbon snugly around billfold to overlap; cut, and staple into a band.