NEW YORK (AP) _ Insurance companies are offering a solution to developers and bankers who find them- selves paying for an unexpected cleanup of property where hidden environmental horrors lurk. Many in the real estate industry are terrified at the prospect of a government order under the federal Superfund Act to clean up an office building or vacant land they originally thought was fine but later discovered was polluted. Companies spend an average of $25 million to clean up a typical Superfund toxic waste site, says Moody's Investors Service. As a result, at least three insurers either are or soon will be offering new policies for coverage of unforseen …