Looking for the correct size for sliding door lock/latch

Question

I ordered part #82-218 Mortise Lock, round face, 3-11/16". The part is unfortunately at fraction too big. I cannot fit it in the door opening. Also, while I was removing the old lock, it slipped into the door cavity and now is gone forever. So I'm without any lock at the moment. Is there a lock that is just a bit smaller? It looks like the distance between the two screw holes is 3 3/4". Please help!!

User submitted photos of patio door hardware.

Paul · Accepted Answer

I think the 82-218 is still the right match, you just have to try to maneuver it in the hole. Check out the video below for some tips on how you can do this.