CROWN SHADES 10x10 Canopy Sidewalls (4pck) - Canopy Walls 10x10, Sidewalls for Canopy - Canopy Cover, Canopy Accessories, Grey

If you want something waterproof, you can get walls made for ez ups (just look up "pop up canopy walls"). I have these and I really like them, because each panel zips to the next one, and you can have a zippered entrance.