Amazon has this highly rated bluetooth FM transmitter for $14.24 when you use promo code 7MZDREFZ
at checkout. This is the cheapest it's been according to camelcamelcamel. Previous low was 16.99. Shipping is free with prime or when spending $25. Also has a memory card slot, handsfree calling and USB pass through charging built in.
BROAD COMPATIBILITY: This bluetooth transmitter works with smart device, like iphone, ipad and android, ipod; and supports AUX input, TF card or MP3 players via 3.5mm audio jack.
HIFI QUALITY& HANDS-FREE CALL: With A2DP technology, enjoy your music via this bluetooth car adapter; Built-in microphone on this bluetooth receiver offers your hands free talking
LARGER DISPLAY SCREEN: 1.44" LED display screen of this fm modulator shows your car battery level when car starts, phone number for incoming calls & name of songs playing.
USB CAR CHARGER: This bluetooth car kit comes with a 5V/2.1A USB charging port, charging your cellphones or other devices via this universal USB car charging port.
EASY TO OPERATION: Plug LeFun FM Transmitter in the car cigarette lighter, control it and the car radio at the same frequency (frequency range from 87.5 to 108 Mhz) and let your phone/audio player connects it via Bluetooth /audio line.