Amazon offers the Polk Audio Omni S2 Wireless Speaker, model no. AM6912-A, for $99 with free 1-day shipping. That's the lowest total price we could find by $51. This compact speaker features a swappable white faceplate, two 2" full-range drivers, two-channel amplifier, and built-in dual-band WiFi.
Orders placed today, December 22, will arrive in time for Christmas.
Update: As a reader found, Polk Audio offers it for $99 with free shipping via coupon code "S2FOR99". Note that it's not expected to ship in time for Christmas.