Well thankfully many foreign food vendors are to be found online and offer a variety of goods. CocoinKorea recently posted about two sites that offer some great finds. I will list those here along with a few others.
They have a lot of your basics like soups, pastas and seasonings. But there is a variety of beauty products as well. What you will notice from some of these sites is that they are mostly selling stuff from Costco. However, as we all know a trip to Costco is expensive and you end up with bulk items. I think this site offers the same stuff but for less and you don't have to buy in bulk.
2. The Underground Grocers "Purveyors of things not kimchi."
This is an online store version of the real one, which is located in Bundang. According to local Bundang folks this is a treasure find for them. As you can see the website is in Korean and so you will need some help there. But if you click around enough you can tell they have quite the selection. They seem to specialize in baking goods (hence the name). But they have a selection of American and Asian stuff as well. The prices seem pretty reasonable too.
I managed to find this one by myself today and I have to say that out of the rest I am really enjoying the site. It seems they cater to the chef at heart with many items on sale that one needs to make specialty breads or recipes. I was going to go to Itaewon today just to get couscous but I am rejoiced by the fact that I found it here. I would say their prices are pretty high compared with the other sites and I have a feeling their shipping charges are a little high too. But I am not sure of the other site's shipping methods. Who cares! After a train ride to Itaweon along with getting a meal there, the shipping costs become almost moot. I ordered from them today and we'll see how the shipping and satisfaction goes. But, I highly recommend them!
I am sure there are more hidden ones out there, and if you know of any others please do share! I mostly got these links from the Yeogiyo site, which has links to other sites which specialize in electronics or clothes.
Seeing all those great things for sale like oatmeal, organic bread mix and frozen green beans made me really happy today. Trust me, I am doing my best to use what I find in my local area, but sometimes I just want a warm bowl of couscous for breakfast.
I hope those sites have something for you~