Amazon offers Sonos Sub Mini Compact Wireless Subwoofer (Black or White) for with free shipping.

Product Description:

Deepen your enjoyment of TV, music, and more with bold bass when you pair Sub Mini with Beam, Ray, One, or One SL. Place it anywhere in the room, breeze through setup with help from the Sonos app, and experience richer, more immersive sound without any buzz or rattle.