Is it possible to convert a USB Port to a Bluetooth connection?

So, the specific case I have is an old radio that is built into the wall and the whole sound system. It has a USB port that you can use to connect your phone to and play music from your phone. My idea is that I could plug something into the USB Port then connect to that via Bluetooth on my phone to play music. I can find several USB devices going the other way where you would plug it into the source, I am looking for something going the other way, where it is plugged into the receiver.