I want to adopt my nephew from Mexico. How do I go about doing that?

I am from Mexico, I have my residency card for the U.S., and in about a year I will apply for my citizenship. My brother in Mexico was kidnapped and his son (my nephew) is now all alone. His mother is here in the U.S. but has nothing to do with her son. He is all alone in Mexico and I want to find out how to bring him over here to keep him safe. I was told that it will cost over $25,000 to adopt him because my brother is missing and his body will probably not be found. (no death certificate). Any ideas on what I can do? No lawyers will talk to me without demanding me to hire them, and I don't want to pay them money if they can't do anything for us. Please help. Thanks for looking!