There isn't a separate part number for the case, so you can't buy a new one separately, and I've never seen just the case for sale used. Mine also did not have a case, so I made one out of some leatherette that matches my interior (the stiffer material provides a little more protection than making it out of fleece). Just sew three sides in a trapezoid shape, and add some velcro on the top or one side.
