Composing : Need rights to a script- how do I get them? by Brian Cheverie

I want to write an opera based on a classic film which means I need to get the rights. The film is an Warner Bros. property and I can't get past their gate keepers to even ask about it. I think I need an agent of some kind, basically someone the people at WB will at least talk to . Any ideas and/or advice will be greatly appreciated.