Customer is difficult
Thanks for writing in! This handle set looks a lot like our 82-086 Legacy Keyed Handle Set. The internal mortise lock can most likely be replaced with the 82-265 Multi-Point Mortise Lock. There is a good chance that you'll need to replace the keeper as well. The keeper can be replaced with the 82-249 Sliding Glass Door Multi-Point Keeper.
I am confident these should be the right replacements but to confirm you'll need to be sure to compare the dimensions for each part; especially the distance between the installation holes.
I'm happy to help! Please don't hesitate to reach out with any other hardware repair projects you might have.
Have a great day!