Rceording audio of Nokia 6300 onto ext recorder

I have a Nokia 6300 with the standard HS-47 stereo headphones.

I want to get an extension lead which will let me record conversations on an external recorder (the voice recorder in the phone too poor).

How would a pre-made headphone extension lead by medified to get me the correct "tap"?

Would all this be easier if I get a blue-booth handset and recorded off that?