Patel Grocery on 4th Ave in Sunset Park is a small gujarati grocery with the basics, including curry leaves and asafoetida and a small stock of vegetables and desi dahi.
In Kensington I like Bangla Nagar on Church, but they dont have curry leaves to my knowledge.
Have you checked out the punjabi places down around Coney Island Ave and Newkirk?
87 Church Ave, Brooklyn, NY 11218
5303 4th Ave, Brooklyn, NY 11220