Looks like Bose stopped suppling spare parts (cable/mic assembly etc.) within one year of the A20 being replaced by the A30. That is not good support for people who bought A20s in the last few years in my opinion. I think for something this expensive they should provide all parts till the headset has been out of production for about 10 years (with 5 years being the absolute minimum).
Buyer beware with Bose!