Button for lock handle in pressed state.
Automatically unlocks when the handle is pressed again.

Also required spring 6.5x10 (or similar) and glue.
Need to drill a hole (d=12mm) in the handle.

WARNING: Using washer with a locked handle may not be safe. USE AT YOUR OWN RISK.

See also: https://www.thingiverse.com/thing:5662873