From the period photos I've seen, the brake hoses were similar to ones I had on a Rickman Trident with Lockheed Racing calipers & master cylinders; they were braided and sheathed in some kind of shiny black fibre reinforced vinyl, which was falling apart on mine. The fittings were also very different to standard Commando, being assembled from a number of parts. Early Ducati 750 GTs with Lockheed Racing kit used the same stuff, so I'm guessing the hoses may also have been Lockheed Racing parts?
I can't find a good enough period photo of the Norton kit, but this Ducati 750 GT shows what I mean. If anyone knows where I can source the correct components I'd like to hear from you!
Black sheathed stainless hoses are available, but I haven't seen those exact fittings. That said, I haven't looked very hard recently.
Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk
This gives all the original PR part numbers. One thing I struggled to find was correct 'tucked-in' header pipes. A certain Emporium north of Birmingham lists them against the PR part number, but when I phoned to order a set I was told theirs were just standard Roadster pipes