Isn't the Filco on the beNippon site simply because xsphat requested it? Why not contact them regarding purchasing the n-key rollover model for you?
I've actually been corresponding with the son of one of my coworkers. He is currently living in Japan teaching English, and he has been kind enough to look into it for me. Apparently the N-Key-Rollover version is can't be ordered from the Diatec web site at the moment.
The english version of the
Diatec page has a very unhelpful "11/5 on sale". I ran the japanese
Diatec page for the n-key-rollover version FKBN104M/EB through a couple online translators, and get the following:
Babelish
"For the stock being cut off, we have stopped the incoming order with mail order at one time."
Google Tranlator
"Stock for the mail order to suspend orders."
The non N-key rollover FKB104M/EB page says:
"We sell this commodity with the diamond TEX online shop"
or
"This product is sold with DAIYATEKKUONRAINSHOPPU"
I've tried to look and see if it is available online elsewhere in Japan, but my Google-Fu kinda falls over when it comes to Japanese. It's all very vexing.

I've toyed with using something like BeNippon to see if they can find it in a store or something however. I may still do that, assuming I decide the Filco is the one I want (I keep going back and forth).