Patio door handles are available online at Lowes.com and at WindowDoorParts.com as of March of 2015. Both websites offer a large variety of sliding door handles in a number of different styles.
Examples of patio door handles advertised at Lowe's include Mortise-style, surface-mounted and flush-mounted handles manufactured by both Prime-Line and Wright Products. Surface-mounted handles manufactured by Barton Kramer are also available.
WRHardware sells both keyed and non-keyed locking pull handles for sliding patio doors. Many other handle models are also available, including internal-latch handles manufactured by Viking and Trimview, a number of Mortise-style handles, and clamp-style handles manufactured by International, Lupton and Northrup.