Greg
I have checked with my supplier of Dynamo's who do have pullies available but the actual pully you have is an AC Company design D60202 so not now made, i believe the Club did have some some time ago, but to reproduce the pulley would require new tooling.
The best solution is to use a separate steel fan with a stock pulley which can be supplied to fit the AC dynamo WOS Performance can do this for you, if you email me i can forward the details to you, i have supplied a drawing of the original AC pulley so they know what is required.
Robin