eBay has the Yamaha SRT-700 TV Speaker Base with Dual Built-In Subwoofers for $109 with free shipping. Retail price: $350. Recommended TV Size: 42-inch or less, mass 30kg or less, leg width 545mm or less, depth 280mm below.
Amazon has the Willnorn SoundPlus Dual-Driver 24-hr Bluetooth Speaker for $11 with free shipping for Prime members or on $25+. Retail price: $50. Has good Amazon Reviews.