Is there a set screw holding the handle on the shaft? It shouldn't be too hard to find a replacement. Remove the door handle, then the two screws to remove the inner cover. Underneath the cover, you should find screws holding the outside door mechanism tight. Somewhere along the way you should discover a manufacturer. If not, a complete replacement door latch should be available. If you take the broken handle to an RV parts store, you can probably just get a replacement handle.
Here's a pretty complete list of RV salvage yards:
RV Salvage/Surplus Yards (List) Updated 2/1/18 - RV Forums - myRVparks.com