I’ve never seen a  ‘made for Sonos’, but that might be because no one has chosen to pay Sonos to use their name? I’d do a web search, and perhaps focus my attention on Subwoofer Mats, but I am only guessing. 

From what I know of the regular sized Sub, such a stand isn’t needed, the sub does not vibrate at all and therefore passes on no vibrations to the surface it stands on. The same should hold for the smaller mini.