Amazon offers Prime members the Mongoose Bike Speaker in Black, model no. MG77776-4, for $10.53 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, shipping costs $5.58. Kmart charges pennies more with in-store pickup.) That's $9 off list and the lowest price we could find. It's compatible with any smartphone or MP3 player and features a mount.