is easy to print and assemble,
has a spring strength adjustable in 9 steps,
does not require any additional parts, just a few drops of lube to start with,
can get locked against re-opening so no uninitiated will know what's inside,
has 31 mm diameter and 52 mm length, but can be scaled up easily.
You'll find detailed printing and assembly instructions https://www.printables.com/model/370915-satisfying-clicking-fidget-button