On my 2007 TourMaster diesel pusher the door latch was worn and out of adjustment to the point of denying access to the coach -- had to crawl in through the driver's window.
I found that the latch mechanism was made by TriMark. I took the internal panel off the door (have to take the window frames apart to do this...) and adjusted mine to work, then ordered a replacement for when adjustment alone would not be enough.
Here is the contact information:
Service & Replacement Parts
1970 N. Linn Ave., Whse L
New Hampton, IA 50659
I will try to attach the drawing of the part -- had to covert it to a PDF.