Local shops sell child locks at insane price - $5-$10 for a small piece of plastic. I decided just to print one.

Doesn't Matter

No

20%

0.3mm nozzle, 0.2mm layer, 3-4 perimeters

• Remove 'mickey mouse ears', Use knife or file to prepare edges
• Put a spring inside carriage (I used spring from a pen)
• Insert button to the carriage. Spring should fit into deepening of carriage and button
• Insert clipping side of the base into appropriate hold of the carriage. Pay attention that button also has clipping that should correspond clipping of the base
• Glue cap to the base - this will prevent disassembly of carriage block. I used small piece of filament to position the cap

Sorry for my English - just see the photos

Just copied idea of factory made lock