I found it on eBay. I thought it would fit ok but actually it's just a little bit too big unfortunately. However, having found the service manual for the unit (if you Google for 'NW-HD5 diagram' you'll find it too) I now have all the circuit diagrams which include the pinouts for the Sony ZIF to CF ZIF adapter. Once I have found the corresponding pinouts for the HDD ZIF, it should be possible to create an adaptor which directly connects the Sony ZIF to the HDD ZIF without an intermediate adaptor. I'll report back once I've made some progress, but it'll be a few weeks before I can look at it again as I'm about to move home. Why? The front panel button assembly is simply glued to the case with double-sided sticky tape. It was easy to prise this off the case and remove it. The whole (very simple!) button assembly then comes apart and the ribbon cable can be extracted. After a few twists and turns I found a Sony consumer goods parts supplier. They are called Seme NEDIS and you can call them on 0870 850 8501 (they have a web site - or a domain name at least - but it seems to be broken). They have been incredibly helpful so far and they're busy tracking down this unusual parts request for me.