Alas, the 1805 French Elites are not particularly well suited for Royalists. You would be better off with the Italeri AWI French (warts and all).
The bicorn was still a cocked hat in 1789 and breeches were still worn, rather than trousers. Officially, the Tarleton combed helmet was specified but not universally adopted. I mounted ESCI British RHA heads on ESCI Old Guard bodies to create Royalist infantry/les blancs of the early 1790's.
If you haven't already done so, why not consider the converged flank companies that served at Jena in 1806? These figures are perfect for them.