Outward opening bedroom door without a lock
I would search Amazon for "portable door locks" and add a long-shackle padlock to this type of device



You need the padlock because the majority is accessible from the outside. The whole thing will obviously be visible and not resistant to detrmined attack.

The lower photo shows how it locks into the door frame, preventing the door opening in its usual direction.

This works because an inward-opening door that an occupant wants to secure while asleep is essentially the same case as an outward opening door you want secured when you are elsewhere. The added padlock prevents passers opening the lock.