Soursop is generally not available legally in the USA and subject to confiscation due to fly larva in it's skin. The USDA checkers at San Juan Airport and other spots sadly pull it from the luggage.
Frozen soursop / guanabana is available at tropical stores as are versions of soursop ice cream at Taste the Tropics and elsewhere. And there's Goya guanabana juice in a can.
No question the slimy, aromatic lusciousness of fresh, ripe soursop is unique and mind-blowing...but you'll have to hire a machete wielding tree climber somewhere in the Caribbean to get it right. I did just that in Grenada and had one big enough to scoop out for weeklong rum drinks at our hotel.