Andersen sliding glass door lock

Sure, take a look at our 82-037 deadlock assembly. I think this may be what you're looking for.

I recommend the 82-043, which is a more modern version of your older latch. 

It's possible that this broke because your mortise lock is fault. It's also possible that it just broke on its own. You'll have to play around with your hardware to determine if the mortise is still in working condition. Try to throw it manually with a screwdriver to test it out. That should tell you whether it needs to be replaced.