Part numbers on the bodies of my rear KONI Adjustables read: '80 - 2180'.
Maybe worth trying KONI again, and quoting that number? You never know - they might have some old stock or a new equivalent that will do the job.....
On a more general note, my experience in dealing with Japanese specialists for these old cars is that you need to actively build up a customer-supplier relationship with them. The only way to get that going - and to distinguish yourself from the numerous dreamers and window-shoppers who tend to contact them with little intention of actually buying anything - is to spend some money with them. Tell them exactly what you want ( in the form of a written purchase order if necessary ) and give them your credit card number. Tell them to ship EMS and charge it to your card. If that does not work with Victory 50, then forget them and try somebody else like Rubber Soul, RS Start or Garage Ishizaka. Don't worry that you might not be able to trust them; they are all reputable and long-established companies.
Nine times out of ten you will tend to find that they are merely shy, or reticent about having to deal in a foreign language.
Good luck,
Alan T.