$19 on Amazon. Voila.
It has two cords, one plugs into the cigarette lighter for power and the other plugs in to the auxiliary port for sound. My car has the aux port and an extra cigarette lighter outlet in the center console, so the wires are all hidden and it looks really neat.
I made two phone calls with it and listened to music and it works great. Only downside is the car stereo has to be in AUX mode for it to work. Oh well. Cheaper and less tacky looking than an aftermarket head unit.