Hi there,
I seriously doubt it. The odd person might have used ones available; other than that, you'd need to look at US sources like MSA/The Z Store. The louvres were very much a US market taste thing anyway.
In general, with Mike Feeney's passing, there aren't any dedicated UK stockists of Z parts off-the-shelf. And even Mike would've been unlikely to have any in stock and would've had to make a trade order from MSA had you wanted some.