Tan Tin-Hung Supermarket
121 Bowery (just below Grand)
This shop looks like just about every other Chinese grocery from the outside, but inside is a well-stocked ethnic Chinese Vietnamese shop.
Along with a huge range of Vietnamese sweets and snacks, there are a number of specialty ingredients for Vietnamese cooking.
The refrigerated green section at the back of the store was a real standout, with pre-wrapped bags of very fresh herbs:
saw-leaf long coriander
a lemon-y smelling plant I believe is fishwort
vietnamese coriander (?)
and some others I can't identify.
There is also good lemongrass, and some sort of long sturdy green aloe-like plant I've never seen before.
Outside the shop they were selling waxy red Java apples, the only time I have seen this fruit in the US.
(Cong Ly is not far from here on Hester and Chrystie. Perhaps this is one of the places they get ingredients from?)