Did you try the Spares Scheme?
I am not an expert on model specs, but I made a batch in about 1970 and supplied a quantity to Tom Ward as I did not want to sell directly at that time. I sold the balance to the Spares Scheme about three years ago.
If this pattern is not appropriate for your bike and the Spares Scheme has no stock, then perhaps you should suggest they consider having some made. Best of luck Roger