How do I increase the height of a sliding glass door lock?
I see that you posted under a carpentry tag. however, my solution would be to find a section of Aluminium Tubing, or tubing profile which fits the "gap" which you describe. 



As  You can see, the example picture is a rectangular profile, which will run the entire height of the door, To fill the specified gap. 

Your problem will be to attach said profile to the side of the slider. essentially the best thing would be to drill into the frame and insert pop rivets, however, there will be a glass pane on the other side of the aluminium door frame, so drilling will be difficult. 

The profile below will allow you to drill your rivets on the side of the door (ie the narrow face of the sliding profile, then you can drill two holes on the top and bottom of the slider (in your photo its the side you can see. 

You will then be able to mount your lock flush to the hinge door. 



Above you can see what I mean. I must stress here, that you dont want to break the glass pane by drilling into the frame where there is glass.