...If only this question could be answered so easily. There are literally hundreds upon hundreds of different representations in existence. The German dramatist August von Kotzebue said that the majority of these depictions are quite far from the truth. He named Isabey's drawing of Napoleon stading near Chateau de Malmaison and the 5 francs coin from the year XII (1804) as being the most faithful representations. Factors such as age and health should be taken into consideration, naturally.
Bonaparte at Malmaison, by Jean-Baptiste Isabey (black chalk drawing, 1801). Here is what the author has to say about this particular piece of art: There, I performed the first full-length portrait of General Bonaparte. From morning to night, I saw him walking lonely in the park, his hands behind his back, absorbed in his ideas and it was easy for me to enter his pensive expression and the appearance of his figure. After finishing the portrait, I presented it to the general: he was pleased with its likeness, he congratulated me mainly for being able to work on it without having to make him sit as a model.
5 Francs coin from 1804. August von Kotzebue: "Each time I see one it's like I'm viewing the Consul before my eyes".