exterior lock for sliding door

Hi,

I am trying to find out if a product may exist that would enable me to incorporate an exterior lock into the patio door pictured here.

The handle and the lock are two separate components. It seems like the easiest thing to do would be to leave the handle as-is, and replace the lock with something new -- if such a thing exists. As you can see, the handle itself has no latch on it; only the lock above it has a latch on the door and door frame.

Thank you very much for your help!
- Matt