Silk top hats are no longer made in the traditional way because the specific type of silk used—"hatter's silk" or "silk plush"—is no longer manufactured.
This rare material was a silk pile fabric with a lustrous, velvet-like finish produced on specialized looms in Lyon, France and parts of England during the 18th and 19th centuries. The last loom capable of making this type of silk reportedly ceased production in the 1960.
So you either have to inherit one or rent one, where formal morning dress is still worn at events like Royal Ascot, you can rent authentic antique or vintage silk top hats through high-end rental services.
Who knew...?.. the things you learn as a writer never end.