There is Hong Kong Market in Grand Prairie. The store has a japanese/korean aisle. Plus it has a frozen section which has frozen dumplings, dons, fish cakes, and noodles. And they have lots of asian vegetables and also a refrigerated section for tofu and dumplings. In arlington about 1 mile from Hong Kong Market is Hiep Thai, it is more Vietnamese and Thai, but they do have a great produce section and also have a big selection of sauces and noodles. Both stores are on Pioneer Parkway.
Hmart in Carrolton is also a great place. It is a Korean grocery but it has Japanese items too, plus a food court. And almost all the stores in the plaza are Korean shops and restaurants.