Microsoft Store offers the Scosche boomCAN Portable Speaker in Black for $9.97 with free shipping. That's tied with last week's mention as the lowest total price we've seen. (It's a current price low for any color by $4.) It features 35mm drivers and a rechargeable Lithium-ion battery, and includes a USB charging cable and a travel pouch.
These tips will leave your ride smelling swell without breaking the bank. Some are also chemical-free.