This article in the on-line NYTimes of 1 April, "For Everything There Is a Season, Even Mangoes", alerted me to the imminent arrival of Alphonso mangoes from India.
The Ataufo (Champagne) mangoes have been around for awhile, Costco carries them, but Alfonsos are rarer here and don't make it into the big box markets.
As I recall some of the Waltham Indian markets should be getting them. According to the Times, "Patel Brothers in Jackson Heights, 37-27 74th Street , Queens, (718) 898-3445, expects to have them for about six weeks beginning April 10."
Does anyone know whom to call in Boston to track them down?