Child door knob cover

My 23 old month son open the door of his room today! lol
Since he sleep in a bed and not in his crimb anymore, he can know wake up and open the door and leave his room! haha (not funny)

I decided to design and print my own.

I initially search thingiverse and found nothing. I search with wrong keyword. Since I am french I did not have the proper way to describe this door knob cover.

here it is, it use M3 nuts and you need to print 2 of them.

Good luck!