Very simple design, but functional: The chairfoot fits a 10mm sphere-shaped chairfoot. The 20mm base fits a common felt-sticker.
This was printed in PLA. I've attached the gcode files that worked for me.
The foot is shaped to fit over the sphere shaped chairbase. If this is just a bit too tight you can heat the model just a bit with a hot air blower.
The author marked this model as their own original creation.