If you find yourself in Recoleta, there are two places that might have it:One is a little shop at Libertad 1157 (between Santa Fe and Arenales) called "Diki."The other is a shop in a galeria just off Montevideo (between Santa Fe and Marceto T.) called Le Gout. The exact address is Montevideo 1079, #27.
I've been to both, and would be guardedly optimistic about your chances of finding what you're looking for. In general, a good place to check for specialty stores is Dan Perlman's blog, Casa Saltshaker. He has this one particular page on which he lists a wealth of food-related resources...http://www.saltshaker.net/buenos-aires-food-drinkThere are several other baking supply type places on that page. Good luck.
At the moment, some of the Carrefours and Discos still have a big Xmas section of turron left....amongst them is a type called "turron blanda de almendras" which is pretty much almond paste. I just bought some today from the Carrefour on Rivadavia 999 (Carlos Pellegrini).
Dona Clara on Corrientes 2561 sells ground almonds (harina de almendras) in case you decide to make your own...
Thanks everyone for your suggestions! Isn't it crazy we have to ask where to find things...so used to just heading to the nearest grocery store and find what I need and once in a while have to go a speciality shop...I have turned it into an adventure instead of getting frustrated....well most of the time, ha!