If you think situation is bad in Brazil you should try finding some of the very easy to find products in Brazil in the USA, like ice creams made of acai, cupuacu, mangaba, nance, soursop, etc. Or juices and wines of jaboticaba, cupucacu, and cashew, which are very easy to find in Brazil. It seems to me that in Brazil there is very good selection of processed products from lesser known fruits, but very hard to get them fresh, unless you go to Belem or Bahia, and even then very few vendors have them. Selection of fresh fruits in big cities like Rio de Janeiro are, like you say, very disappointing.