I got a k850i earpiece as recommended but found that the case wouldn't close properly with it in, and as a result the screen lock button didn't work. This was after some filing of the component; I couldn't see how to do any more without wrecking it.
I then realised that Defy earpieces are now readily available on eBay and have one of those which works fine at least for the time being.
 Also, be careful not to loose the plastic volume / lock buttons when you take the case apart....
Last edited by xinaesthete; 9th March 2012 at 04:44 PM.