RTL 510 Rubber piece replacement

Hey everyone,

it seems that I have misplaced my seatpost rubber piece (the one part that goes in between the mount itself and the seatpost so that the light won't slide or turn on the seatpost).

I have checked some stores, but they only sell the complete mount for the varia for about 20 EUR, including a second mount and another aero piece that I never needed in the first place. This is too much money for three pieces of which I only need one. Does anybody know if there is a rubber piece like this being sold somewhere separately?