Meritline.com has the 2 Pack Meritline FM Radio Pen (88MHz to 108MHz) with 4 Button Cell Batteries for $8.99 - $6 rebate (Exp 09/30) = $2.99 with free shipping.
Includes black ink cartridge and 1 blue refill. To replace ink cartridge, remove lower barrel by pulling straight down, then unscrew old cartridgeAuto-Seek Tuning: Each touch of the button locates a new FM station.
