As far as I'm aware only a small number of the connectors were made in tokyo then sold onto harold wood of seiko Australia. He then outsourced the development of part of the cable that converts signals to rs232.
The cost of the cables is expensive. When I bought mine I was told it was one of the last to be made as the number of connectors left are very few. email rod on the address above to find out more. If thats no use I have harold woods email but he seemed reluctant to suply me one as I'm outside australia.
If your interested in a bit of a project to produce some then I have some plans from seiko on how its done (as well as the working article).