Could it be something like this? Found this on Amazon for a 3-Pack:
Headphone 3-Pack AUX Headphone 3.5MM Extension Cable
I don't think that cable is the actual Bluetooth Transmitter, the cable is more of a pigtail that extends the transmitter so that it can be a little more flexible in placement. You could also be fancy and use a right angle hack to minimize it from jutting out too much when plugged into the scanner.