Tightening my elastic strap two holes worked for a year or so, but eventually the elastic lost it's elasticity. We bought a pack of bungee cords last week which came with a bunch of 8-12" mini bungees that were about perfect for this. I cut the metal hooks off and melted the edges. We sewed one end to the fabric piece and the other end I just tied a knot in one of the existing button holes so we could adjust the length. Working well right now, hopefully stays that way!