I got mine about 4 years ago soon after I got the car and changed my phone. Back then vRStu was doing them which is where I got mine from. Think SteveP might be able to get them.
The part number on my control unit is 1Z0 035 729. I'm sure there is a newer version out now though. I haven't got the part number for the mic or looms to hand, not sure if you can buy the loom or need to make it yourself. Mine came as a whole kit. I have seen the whole kit on eBay.
My car is a 2006 and the kit works with RCD500, RCD510 and RNS510 and any Bluetooth phone I've attempted to pair with it!
Hope that helps a bit
