Louis Edouard Bignon, one of Napoleon's diplomats is acknowledged to have collaborated on the yearly Precis that Napoleon would make to the Senate on the state of France, especially regarding France's relations with foreign nations. (It would have been equivalent to the US President's 'State of the Union' speech he makes to Congress every year) After Napoleon's abdication Bignon proceeded to write a 14-volume History of France from 1799 to 1815. My sense though, is that in the early 19th century, such ghostwriters tended to be unaknowledged, so it may be tough to identify them.

-Alex