Thanks for writing in to us! The lock plate from your mortise latch looks a lot like the one use on the 82-211 Mortise Latch & Keeper. To determine if this is the right replacement, carefully look over the dimensions shown below. This lock is compatible with the 82-033 Patio Glass Door Handle Set.
To replace the lock cylinder there are two possible options available. You can either purchase the entire exterior handle, part 82-306 or purchase just the 82-310 Key Lock. You'll likely need to cut down the spindle for either replacement to properly install them. Take a look at the tagged tutorial
Take a look to see which may be the best option for your repairs.
Thanks for confirming this information. Your mortise lock appears to be similar to the 82-214 we carried at a point however it has been discontinued and the design of it has changed slightly.
The new replacement is the 82-214B but it has installation hole spacing measurements of 3-13/16", which is just shy of the 3-7/8" measurement yours has. That said, I'm afraid we would not be able to supply you with a suitable replacement for your existing mortise lock.
You may have some luck a local hardware store but I cannot make any guarantees. Our sincerest apologies that we cannot be of more help with your repairs.
