I don't think there one thing that everyone has to buy from each of the countries. If I was you, just browse around. If you do find something you really like, have some fun and haggle the price with the owner. Thats considered an art form there and can be fun.
Life is too short to let the ship of your dreams sail without you.
Carnival Destiny Feb. 2006
Carnival Fascination Feb. 2007
Royal Caribbean Grandeur of the Seas Feb. 2008 The DTW & MsBJ tour
Carnival Valor MsBJ and Dina Feb. 2009
Carnival Glory MsBJ and Dina Feb. 2010
Carnival Dream MsBJ and Dina Feb. 2011