The closest to that area I can think of which is a proper large Asian supermarket stocking akin to the ones in Chinatown ( ie stocks frozen / fresh / cooking utensils is on Walworth Road next to the Dragon inn restaurant ( opposite Elephant Rd ). It also has a small Vietnamese restaurant incorporated into it. There is also another one on the second floor of the E & C shopping center which is large but not as well stocked. TBH I was surprised when such a large one opened there but its not short of custom.
Depends what you are looking for, there is the big one on walworth road, although Vietnamese stocks most asian cuisine. There is also a small Vietnamese shop down the blue and a shop on old kent road near to asda. Of all three I prefer walworth road