Is there a reliable (and ideally, easy to construct+tune) method of measuring inertial mass without using gravity (e.g. weighing on a scale or a freefall apparatus or a pendulum) or rolling (e.g. pushing an object and seeing how fast it moves horizontally) for sphere-shaped objects? The rolling requirement is because the spheres I'm using will have non-uniformly distributed mass (some may be hollow, some may be hollow, some may be solid, and some may have masses symmetrically (dodecahedrally or icosahedrally arranged weights) placed not at the center but not at the outside (effectively comprising a shell of high mass between two lower-mass volumes when viewed from the radius out.)

I'm attempting to compare the inertial mass of each sphere (same radius and same gravitational mass for each) while excluding gravitational effects (gravitational mass and moment of inertia) from the experiment.