for USA, you can also shop online at:
and ebay also has some items.
don't forget you can grow a lot of things yourself, too.. here's some seed companies that sell asian seeds:
for korean/japanese sweet potatoes: http://www.sandhillpreservation.com
don't forget you can buy things on ebay as well.
you can also go to gardenweb.com & join the asian vegetables forum, as well as the seed & plant exchanges and see if anyone would like to trade with you.
you can also make your own soy milk and tofu.
you can buy up to 30lb of non GMO (genetically modified) soy beans here: http://www.tosteds.com/products.asp?cat=11
here's a soy milk maker: http://www.soymilkmaker.com/soyapower.html
here's a tofu kit that comes with a tofu mold and enough natural nigari to make 240 POUNDS of tofu. http://www.soymilkmaker.com/tofubox.html
hope this helps some people.