The Usuba has been the hardest one to find what I want. Specially for the steel, it seems that there are not many high end White Steel #1 Usubas, besides the Masamoto KS. But that one is not available with octagonal handle.
https://www.knivesandstones.com.au/collections/usuba-vegetable
There is a decent chance that James will put whichever handle you want on it if you ask nicely.