I do not know of any RCA converters that utalize the factory cd plug, but there are many that you can use that require you to tap into the speaker wires. Nice and simple to do. If you need one I have an extra just laying around the house.
<span style='color:gray'><span style='font-family:Courier'>1995 e36 3 Series RIP
1999 e46 3 Series BURN IN HELL
2000 MR-S Roadster= Current</span></span>