Lowe's and The Home Depot both sell replacement patio screen door parts. All About Doors and Windows is another retailer that offers parts for patio screen doors.
Another option to locate replacement parts is to contact local hardware or door and window stores. eBay and Amazon both carry the parts online. The selection varies depending on the size and the brand of the door. Some screen door companies offer replacement parts for their products. In this instance, users can contact the manufacturer to inquire about replacement parts for their exact product. In some cases, the doors may even be under warranty so that parts are free.