Upvote:7
There are a lot of musical instruments shops at Rua da Carioca, downtown. You can find a cuΓca there. Also, downtown is certainly a destination for tourists, so he's probably going there anyway.
For example, Casa Oliveira de MΓΊsica is located at Rua da Carioca and in their website they claim to sell cuΓcas among many other percussion instruments.