Charles-Ferdinand de Bourbon, duke de Berry popped up on pages 152-154 in Journal of the Waterloo campaign ... 1815, Volume 1
By Alexander Cavaliť Mercer; where the Duke, near Ghent/Brussels is described as training a cavalry troop of about 200.
Thought it was interesting that none of the easily available biographical accounts of the Duke make mention of this. The standard line is that he went to Ghent after the French Army deserted him for Napoleon; but none make mention of his establishment of an anti-Napoleon French cavalry troop.
One of the latest books that covers the Duke's assassination in 1820 even has the Duke traveling back to England in 1815.