There are many Taiwanese, Korean, Chinese and Japanese residents in the DR, thus the ingredients for many of their dishes can be found here. One of the better places for Japanese ingredients, for instance, is located next door to the Supermercado Popular of Calle Privada corner N??ez de C?ceres in Santo Domingo. I don't know the name of the place, it is located in the first floor of an apartment building. It doesn't look like a store, but when you walk in it is a small grocery store, which has a second room in the back with more grocery items and a third relatively large warehouse and cold storage room for vegetables.
Also check out the Chinese food store on Maximo Gomez, about a block or two from the Supermercado Nacional, on the eastern side of the avenue. And there is another Chinese/Japanese food store on Romulo Betancourt Avenue, from Winston Churchill before N??ez de C?ceres, but sorry, don't know the number or the cross street.
Check out the Loto vegetarian restaurant on 27 de Febrero for Taiwan food, and the Ariyang Restaurant, also on 27 de Febrero Avenue, for info on Korean ingredients.