Thanks for that David and Steve (and for your replies on the Facebook forum).
It seems the only options are to wait for the item to turn up on ebay, if the thing doesn't crumble into rust before, or have it manufactured.

I suggested a group order since there is obviously some demand from a number of owners. The question remains, what supplier to choose from? The name PowerFlow came up on the forum, no doubt there are others.

For those of us on the Continent there may be additional options. Nicolas Barat suggested a French supplier located in Moselle, in Northern France:

https://www.jgperformance-57.com/fab...ent-sur-mesure