Try Melvyn Rutter. He often has the elusive parts.
Also, MMC fitted steel wheels to the Anniversary series that was marketed around 2006 - not sure if this is relevant but it may help.
Tried MR but no joy,
The Anniversary model had a 5 stud wheel. They're apparently no longer available either!
One option is Image Wheels, who'll make a bespoke wheel, but at a price!