Mexican crema / sour cream
Mexican crema is a cultured, pourable cream, milder and thinner than typical sour cream.
Mexican crema is usually found only in Latin American shops or by mail order, while sour cream is in every supermarket. Its higher fat content keeps it from curdling in hot dishes, and it can be drizzled over tacos and enchiladas.
Substitute:
Crème fraîche thinned with a splash of milk or a little lime juice comes closest. Sour cream also works but tastes tangier and can curdle when heated, so add it at the end or cold.