These parts are available on tunze.com, I attach the links. it would be unusual to need these parts unless you lose them, keep in mind the rubber pieces are not in a perfect square, this is intentional so the magnets are lined up to minimize the interference with the motor, if you have the clamp rotated 90 degrees it wont be secure. If the clamps get stretched, which is unusual but can happen from frequent removal and reinsertion or movement, you can soak them in hot water, squeeze them together and then dunk them in cool water to tighten them back up. Usually the only issue is that all 4 rubber pieces are not fully inserted and these should touch the back of the pump and act to hold the pump.
https://www.tunze.com/US/en/details/6025.630-silence-clamp.html
https://www.tunze.com/US/en/details/6020.620-silicone-buffer-14-mm-055in.html