Hmm... I thought Cuatros were mainly a Puerto Rico thing (or caribbean).
But you may want to try mercadolibre.com.ar for charangos. Some of the larger vendors there usually have store fronts which you can check out (once you make an offer to buy and get their address) -- ask first.
West of 9 de julio, Sarmiento and its surrounds is the musical instrument centre of the city. You will find plenty of those instruments around there but because these instruments aren't really native to this area, only a few of the local builders are making them and the rest of what you find will not be much better than toys. Persevere and you will find good ones but they won't be cheap. Are you travelling elsewhere in South America? If for example you are going to Bolivia you will find lots of charango makers near the witches market in La Paz giving you much better choice of well-made instruments at reasonable prices.
Thanks. Unfortunately we will only be in BA for four days and then on a cruise
to Antarctica. I have seen several interesting instruments advertised on mercardolibre and hoped that I could find some at a shop in BA. Where I live I have no chance of even seeing one of these instruments to see how they play. I am looking for a decent instrument. I will try to contact a few of the sellers on mercadolibre as well as walk around the Sarmentio area. Is there a particular store I should find?
Montevideo corner Sarmiento (2 blocks away from Corriente y Callao). You'll find all the instruments you need there.
Indeed many music stores along Sarmiento from Montevideo to Libertad where the music district ends and the gold and jewelry district begins.
Sorry to drag up this thread but did you (or anyone) ever find a cavaquinho here in BA? I have a friend is visiting next month & is looking for one. My husband is going to Brazil (Santa Cruz) next week. But I don't know if he will have time to get one. Any idea what kind of price these things go for? I have no idea. I'm guessing they are probably in the same price range as the charangos.