Guanabana / Soursop in NYC
The fresh fruit I can't say, and in New York I can't say, but I do know something interesting and relevant. GOYA puts out a line of frozen fruit nectar concentrates, a limited tiny line that in Chicago is sold only through one small chain that has only about five stores. Otherwise, the many GOYA outlets in town do not carry them. I don't know why. I do know that I got my supermarket manager to order me some and that worked. One of the nectars is guanabana (soursop). If you want the fruit for its flavor or for some particular nutrient property and can't find the fruit, the frozen nectar might meet your need. Find a supermarket that carries any GOYA product and see if your store manager will order what you want; you might have to take a dozen cans. BTW these frozen nectars (they have several tropical fruits) are much better than the canned and are very good as a mixer with rum.
Try Caribbean Food Market
1303 Fulton St
(between Nostrand Ave & Verona Pl)
Brooklyn, NY 11216
Call them during normal daytime hours and ask, they should have guanabana. Get back to me if they do have some.
I was in Jamaica in May and fell in love with guanabana. Fun fruit to eat. and it is suppose to "make you very skinny" according to the jamaican lady who sold me it at a local fruit market in Negril, Jamaica (picture attached)