Based on the dimensions you could choose either of the following Sash Locks. These vary by the number of levers, the higher the levers the more secure the lock is.
Union 2295 - 2 Lever Sashlock (76mm)
Union 2243 - 3 Lever Sashlock (76mm)
We would generally recommend the 2 Lever lock for a bathroom and the 3 Lever lock for any other internal door.
Anthony N