The low volume on your audio recordings might be because the FP1 has a secondary microphone on the top end as well. So the recording might have just been what the secondary microphone picked up. Try recording again with the secondary microphone held shut with your fingertip.
The microphone sits on the daughterboard which is unfortunately permanently out of stock in Fairphone’s shop. I think you will have a very good chance though if you create a “buy” topic here in the forum’s unofficial market.
If there is a Fairphone Angel nearby, even better – there is a good chance they might have this spare part for you. It is rarely looked for.