Hi Kev,
You're right not to abandon this guitar! But I'm confused (not an unusual state for me). You mention "a seventh string"? Is this a 7 string model??
Assuming it's a 6 string, you're not likely to find an OEM part unless a member has a spare to offer.
The closest bridge design match that I have on any of my guitars would be the Vantage VP710 so I can't speak authoritatively, but looking at the catalogue pictures I would not expect that it would be difficult to find a replacement saddle (or more likely, a full set replacement for aesthetic reasons).
http://www.matsumoku.org/models/ariaproii/ys/ys.htmlThe main thing to keep in mind would be the saddle spacing which should be 10.5mm IIRC.