Over harvesting of sturgeon for their eggs led to near extinction and they became a protected species. Evidently, they haven't bounce back as anticipated so caviar is still produced at a relatively low level in the US., keeping it a "rarity". A shame since who doesn't love a fine cracker with caviar before a game?
If caviar isn't your first choice, you might consider sour candy. I'm not much of a hard candy/sour candy person, preferring chocolate almost exclusively. I did love licorice as a kid - not sure where that craving went. Do you have a favorite sour candy? Flavor?