[Arran]

I don't even think that you need a diagram for this thing, it looks like standard straight line TRF set, a couple of micas, some interstage transformers, coils, a grid leak, and a paper cap. You could likely use one for another set with the same tubes and find 95% of what you need. I would try contacting the company yourself about their radio business, sometimes employees make up stories like that because they can't be bothered finding out.
Regards
Arran