Not every operator is insured or has an AOC that covers that part of the world and not every broker has operators on the books that have that insurance or AOC coverage.
Just a matter of making phone calls till you find one that does. I don't know any of the top of my head, did you try some of the bigger brokers such as Airpartner or Air Charter Services? Alternatively did you try any of the web based quoting companies such as Avinode or CharterX? No point calling the little guys, go enquire with the big boys, your chances of success will be that much greater.