I was having a quick look at some of the proxy companies that I know of, to check if they deal with paper models.
But I think they mostly deal with figures and anime-related merchandise.
The one that apparently helps with biding to auctions and buying from Amazon.jp
and other sites, and that helps with non-anime merchandise is this one:
paper model search results | FROM JAPAN
I have never tried this one. But maybe some one can have a deeper look at it and see how it works.