About twenty plus years ago the 911040 seal was NLS and I had feelers out trying to find one from multiple sources. They must have decided to start making reproduction seals because all of sudden a couple of years later I wound up getting three of them from different outfits, TRF, Rimmer and Classic Autosports in Inverkeilor Scotland in a one week period. I used one and gave the others away to people I knew that had hardtops for their late Spitfires.
For the side window seals, they too were NLS but they were made up from the same fuzzy windlacing material used as door seals. I got a couple of the fuzzy door seals and carefully cut and sectioned them for a good fit up to use as side window seals. Just looking at the Rimmer Bros listing, they are doing something similar rather than supplying the preformed and fitted LH and RH seals.