Any other modder correct me if this is a bad idea, but what you could do is extract the default Bith lip sync files. These lip sync files can be found in the lips folder specifically inside the "localization.mod" file.
This file can be accessed via ERFEdit, once inside you should be able to see all the vanilla lip sync files for alien VO. All you'd need to do is extract the Bith lip sync files and place them in your Override folder.