Hey there are a few specific ingredients I'm looking for, and I'd like to find them in my neighborhood (Upper West Side) if possible. I talked to a chef I know, and he told me my best bet is to try a Japanese and Peruvian grocery store.
The first is "Sake Lees Vinegar" (in Japan it's called Yusen Su). Basically a vinegar made out of the "lees" (a solid product that site on the bottom when sake is created).
The second is Aji Panca and Aji Amarillo. Basically a peruvian pepper paste. Can't find these things in any store in Manhattan.
Here is an example of the Aji Amarillo: