If I'd been shopping for produce and not a backpack snack, Kam Man would have been just the place to pick up wing beans, or murcuots, or generous plump sapotas. As it were: K Fat brand "sweet and sour sesame peanut candy" (12 oz., about $2), from Vietnam, lists soursop as its first ingredient. Without the label, you might not identify the fruit, but you'd have lots of time to chew it over the possibilities; they're very firm.
Kam Man Marketplace
219 Quincy Ave., Quincy, Massachusetts
(From a September 2011 visit)