Replacement door handle w/lock

Looking for replacement handles or locking mechanism. This is a very old glass sliding door handle. It is flush mounted, and when you slide the plastic locking mechanism... it pushes a plunger-style pin out of a hole on the back side of the door frame and into another hole on the adjacent door frame which is behind it... which then creates a lock - as the pin has now come from the lock, thru the door frame, and into the next door frame. That prevents the doors from sliding apart. It's a plunger style locking mechanism, activated with the slide of the plastic lock button. Any help would be appreciated. This is a large office building... and almost every slider in the 18 story building needs new handles.