Sunvalley Brands via Amazon offers the TaoTronics Optical and Aux Bluetooth Transmitter Receiver for $49.99. Coupon code "C9CBBPRE" cuts it to $36.99. With free shipping, that's $13 off and the lowest price we could find. It features Bluetooth 4.1, 3.5mm aux jack, RCA inputs, and up to 15 hours of use per charge. Deal ends March 31.