See the RESOURCES button on the toolbar - there is a whole list of RV parts & salvage places.
If you can find a brand name on it anywhere, maybe the key slot or on the back, you may be able to get a lead from the manufacturer. Trimark & Bargman are the major brands on RV entry door hardware, but they don't seem to have this one.
We had a latch like that on a late 80's vintage trailer, but I haven't seen one in many a year. Good luck!