LightInTheBox offers the MiNi Portable Wireless Bluetooth Speaker in several colors (Blue pictured) for $5.99 with free shipping. (Choose "Postal Service - No Tracking" during checkout. Bowen20112012 via eBay charges about the same shipped.) That's the lowest price we could find by $2. It features a 280Hz to 16kHz frequency response, Bluetooth 3.0, 3.5mm auxiliary input, TF card slot, titanium alloy shell, and built-in rechargeable Li-ion battery with up to four hours of music per charge.

Note: This item ships from China and may require three to four weeks to arrive. Uncheck "Add shipping insurance to your order" during checkout to remove the 49-cent fee.