Universal Hardware Universal Hardware Occupancy Indicator Deadbolt, non-handed, adjustable backset, Satin Chrome Finish UH40131 - The Home Depot
Commercial Grade Bathroom Door Handle Lock with Occupancy Indicator - See Occupied Vacancy or Engaged Status On Public Restroom Toilet Handle - with Deadbolt Locks - Amazon.com
"Open","Occupied " indication Wave Lever Handle Door Locks for Bathroom Toilet | eBay