I was offered this bike a few months back, now I think of it, it was probably a year ago. Not sure where I saw it or the history.
I too have a a 93 NX5. Like you I was thinking of converting mine back to 93 spec (it currently has ram air etc). I have the front fairing, tank and 'airbox', but a seat has eluded me. Airtech in the US sell them, but it's pricey to ship over to the UK. I did actually have a 93 seat unit that came with my 92 NF5. I sold it to someone at Fastline about 18 months ago. Perhaps I could email them and see if anything happened to it and if they would sell it back.
I've dealt with Fernando Mendes (ex GP125 racer) before when ordering the fairing's for my NF5. Really nice guy and he might be interested in making a mold.