Ladies and gentlemen, this is what I call an "eBay feeler".  You go to eBay, go to the auction list for Magic the Gathering and type in "Chinese".  Now you look at the results, and pay careful attention to the *locations* of the sellers.  If they are in foreign countries the name of the country will appear under the price.  You want a seller who is in China, or Japan, or Singapore.

When you find a foreign seller who has a high feedback and a lot of auctions (or even better yet an eBay store), you have located someone who is (a) reliable, (b) makes a living selling MTG online, and who is (c) on the ground in the country where the foreign cards are being sold.  Then you send him a message like this:

Hi. I noticed you are selling foreign magic cards on eBay. I'm trying to collect 1 mint copy of every printing of the card Stone Rain in each language. I still need:

Simp. Chinese:
8th Ed Foil
9th Ed
9th Ed Foil
Ch. Kamigawa
Ch. Kamigawa Foil

Japanese:
8th Ed

[... etc ...]

Do you have any of these Stone Rains (mint cond.) that I can buy? If not can you suggest someone else who might? Please contact me! I live in the USA, and can pay via PayPal. Thanks.

- Chuck Seggelin; The Stone Rain Project; www.plastereddragon.com/srp

Now you wash rinse and repeat.  And make sure you keep a list of the sellers you've already contacted so you don't keep pestering them.  If you are lucky, you may get some promising e-mails back right away:

Hello

I will try to find
Simp. Chinese:
8th Ed Foil
9th Ed
9th Ed Foil
Ch. Kamigawa
Ch. Kamigawa Foil
for you.

May be take a few days.
Can you tell me how much are you willing to pay for these S-Chinese Stone Rain.

Thanks!

Ahhh.  Reminds me of the time I knocked off an entire language in a chance encounter with a Singapore-based eBay seller.  Hopefully something good will come of this!  Wish me luck!