Did you find one? I just bought one on Amazon for about $35.
MX5-FRDR is the same as a FRDR-AUX, but with the addition of a 5vdc output connection. It was originally intended to connect to a satellite radio receiver, but you can just ignore the power connection and use the input.
I'm using the 5v output to power a bluetooth receiver that is connected to the input. I then stream audio and phone calls through the bluetooth receiver/FRDR into my audio system.