There are several styles at Amazon. Try this link:
https://www.amazon.com/slp/rv-door-h...dskadww6nvh7tu
Remember, if you do install anything on your trailer sidewall and the door facing, make sure the screws/rivets are inserted into a structural component. The thin plastic/aluminum skin on the outside of the door and the thin aluminum skin/FILON sidewall of the trailer will NOT hold the screws if a gusty wind hits the open, latched door. It'll rip the screws out of either the door or the sidewall. It (the screws in the weak parts) also won't "survive" the first kid that closes the door with the latch in place....
Alternative: Install the "door part" near the lower edge, and into the door aluminum frame and install the "trailer part" just above/below the J-wrap, there is a strong structural component just behind where the J-wrap is attached to the trailer.