Guessing you're looking for an 8/57 x 19. There's normally several on ebay being punted out by trusted sellers. I'd contact Jasmine Porshalink or 9Apart (formerly known as Porsh-apart) direct to see what they can do for you. Would be surprised if Brian at Jasmine didn't have one.
Might be worth calling Chris Weaver (Exel Wheels) too. I'd be surprised if he couldn't find one for you. It would also be a great opportunity to have your wheels refurbed (and colour changed - anthracite, for example, looks really good on the 'lobster fork' wheel).
