Trying to Find Correct Mortise Lock for Sliding Door

To whom this may concern,

I bought a 3 inch 11/16 inch ... 3/16 lock and it's the correct height, however the back of the lock does not fit in our sliding door. The mortise lock hole in our sliding door is oval shaped, and not rectangular. I attached pictures to this email to better help understand. Is there a 3inch 11/16 ... 3 inch 3/16 mortise lock that has an oval shaped back that can fit into this sliding door?

Thanks,
David