Just rubber feet! Either for replacement parts or customised for a certain project.

The included models were measured from some original parts and copied with FreeCAD.

The OpenSCAD generator script creates more simplified feet, but with any shape, size or screw fitting required.

Unless particularly stiff feet are needed (for instance, for a heavy appliance,) try printing with the softest flexible filament you have to start with. 

Experimenting with varying amounts of infill and perimeter counts can also make a lot of difference to the final rigidity.

If printing a soft foot with sparse infill, it may be wise to reinforce the region that takes the compressive load of the screw head with full infill as a cylindrical modifier (see image and included .3MF file.)

TPE filaments tend to be less slick than TPU, so may be more suitable.