I did find some by-the-meter, on-the-roll on ebay as well. Multiple sizes, including 35 mm. Again, overseas, but there's no way around that with this strap width. (Looks like they might be out of stock soon, though... But given how much they have sold in the past, they might have more in the future. I went ahead and got myself some.)
As for the discussion, I have to agree that it looks like the 1.5" cotton webbing used on the thigh boxes, between the front and back pieces of the armor. The 45 mm might be a good compromise between that and the current 2" standard, but it's even harder to find than the 35 mm. To that end, I'll throw my proverbial bucket into the same ring as Pandatrooper and batninja; it would seem more logical to assume imperial widths on the original costumes since they were mostly likely made in the US. Then again, assumptions can be dangerous. Lol.
Don't you guys wish we could just hop in a DeLorean and go back in time, measuring tape in-hand?