Here are some ideas on where you can find these items -
[background=rgb(252, 252, 252)]Dijon mustard - I have seen national brands here in large supermarkets, and specialty brands in Chinatown[/background]
[background=rgb(252, 252, 252)]worcestershire sauce - I have seen this in Chinatown many times[/background]
[background=rgb(252, 252, 252)]horseradish - in a bottle you can find this at kosher supermarkets around the jewish holidays in Belgrano and around Once[/background]
[background=rgb(252, 252, 252)]balsamic vinegar - easily available, many brands, different qualities of product, here it's called "Aceto" (pronounced ACHETO)[/background]
[background=rgb(252, 252, 252)]brown sugar - easily avaible at any dietetica (health food shop) there are 2 kinds - called "azúcar rubia" (light brown) and "azúcar negra" (dark brown)[/background]
[background=rgb(252, 252, 252)]good chocolate candies - there is chocolate of every description here, not that great though, if you want better quality chocolate go to a confitería and buy "bombones" but they are really expensive now, around $400 pesos / kilo, lindt and those European brands can be found in Chinatown and in large branches of Jumbo and Disco supermarkets[/background]
[background=rgb(252, 252, 252)]dill - it's called "eneldo" en español - they have it in some better verdulerías fresh, but you have to ask for it, they keep it in the cooler, and dried you will find at some dieteticas[/background]
[background=rgb(252, 252, 252)]tumeric - called "curcuma" en español - almost every dietetica sells this spice[/background]
[background=rgb(252, 252, 252)]lovage - I have never seen this in Argentina, but I am sure it can be found somewhere, it's called "apio de monte" en español, not to be confused with "apio" which means celery[/background]