Im afraid I cant help you with a local contact in the Wine Trade.... but if you are staying at a large chain hotel, I would say you get the Concierge to do a little homework for you.

I would do a little expectations management as not too many bodegas are available in Japan.... but you may be able to get a few labels from Catena, Trapiche, Achaval Ferrer and maybe Terrazas de los Andes.

Also, if you care to PM or email me, I can provide you with more information on an alternate solution that may be of interest to you.... this would make it possible for you to get any wine produced in Argentina delivered to your doorstep.