There is no good way to do this, and it may not be possible to get the will. Wills are not filed until a person dies and they are probated; there is no central file or archive for unprobated wills. Prior to that, they are kept by the testator (person making the will), the lawyer who drew them up, and anyone the testator voluntarily gave a copy to. If you mother's copy cannot be found, if she did not give a copy to anyone else, and her lawyer's copy cannot be found (which may be the case--he might not have kept it, or it could be lost among all his files) then you will never locate it and so it will have no legal effect. All you can do is try to get it from the lawyer (or from any attorney who make take over his cases); to speak to your mother's accountant (if she had one) and any siblings (since she might have given them a copy); and look again through all her papers and effects, including in any bank safe deposit box.