Frost King 13.5-in W x 24-in L x 0.031-in Washable Cut To Fit Air Filter in the Air Filters department at Lowes.com
Amazon.com: Frost King ES1550/6 Window Air Conditioner Electrostatic Filter, 13.5" High x 24" Wide x 1/4" Thick, 1 Count (Pack of 1), White : Home & Kitchen
Amazon.com: Frost King, Window Air Conditioner Filter : Home & Kitchen