Broken door latch
Hello and thanks for contacting SWISCO. Take a look at the 82-043 Andersen Tribeca thumb latch replacement and see if matches the dimensions of your old part.
I see you already were looking at the 82-037; your mortise lock is indeed an older version of it. If you're unsure whether your mortise lock needs to be replaced as well, try manually testing the mortise by removing the handle and inserting a flathead screwdriver into the mortise hole. If you can manipulate the locking latch with the screwdriver, the lock should still be fine. If you can't, then it indeed may need to be replaced.
Great! Let us know if you have any other questions. Happy holidays.