Good news, as you can see (and hear) in the above video the Sega Microphone has been repaired using a $10 part from eBay. A marvellous success! The particular type of microphone cartridge was a 600 ohm Impedance Dynamic Microphone Cartridge Black BG-58. I hope if anyone else out there needs this they will find it in the course of their journey.
In other news I have received another ASUS K7-class motherboard today with a 900MHz Athlon attached to it. Looking forward to testing this later in the week as well.