I have the exact same stereo and the same problem, however,
I dissected the front speaker din wire and can tell you what it looks like: the core/center is two very skinny wires yellow and white and they are wrapped in copper wire inside a white insulation tube. Then outside of that is one skinny red wire and all is wrapped in copper wire with the outer gray tube.
I suggest getting the converter if that is possible.
The only reason I am trying to use this relic is because a low life stole

my ALPINE CDE-9845 and I have had issues with the last 2 freebie replacements.
Let me know if you find a harness for this..