Costco is another good place to get foreign foods and other stuff in Kansai. It is located in Amagasaki which is about 15 minutes away from Osaka (Umeda) on the JR Hanshin Line (between Kobe and Osaka).
Costco is good for some things, like buying in bulk, but if you are looking for just a few items it may not be worth the effort.
Where Costco shines is in the goods! If you are looking for items other than food, then Costco will be the place to look and as always the prices will be quite reasonable.
