Existing Patio Slider handle. No identification found on door or frame, etc.
I'm afraid that I can't say for sure what will work. That depends on two important details: the keyway in your mortise lock and the hole spacing of your handle set.
For the first detail, look at our 82-265 for an example. You'll note two 45 degree slotted keyways near the center of the mortise body. A 45 degree slot is pretty standard for this kind of door, but you should check to make sure.
I would also confirm what your hole spacing is. Measuring from center-to-center, I think yours should be 3-15/16".
Assuming my assumptions are accurate, you can use our 82-044 handle and an 82-316 key lock. We even have a video on how these two parts install on doors similar to yours. But like I said, it's best to confirm all details before you buy anything.
Great! Let me know if anything differs from what I outlined. I'm happy to find a better option if necessary.