As for those who'd like to know what (former) Guard members belonged to the "Battalion de l'île d'Elbe" and the "Escadron Napoléon", Marco de Saint-Hilaire has compiled a list of names:
link
However, this list appears to be incomplete and the names may not always have been rendered correctly. Presumably, the only way to get to know all names would be to compare Saint-Hilaire's list with the registers at Vincennes concerning the Old Guard grenadiers, chasseurs, Polish lancers, and attached units (an extremely laborious undertaking). Members following Napoleon into exile would have received an accompanying comment to that effect.
I tentatively spot-checked just a couple of pages from only two registers.
First, from register GR 20 YC 160 "3e régiment d'éclaireurs, attaché au 1er régiment de chevau-légers lanciers "polonais" de la garde impériale, 1er janvier 1814-21 mars 1814 (matricules : 1 à 957)":
Manuscript page 96 = digital version page 100 (enter "100" into the white field in the lower right): "N°. 478, Bielinski, Joseph Antoine", with the following comment in the column at the right: "Parti Pour L'ile D'elbe Le 11 avril 1814".
This person may or may not have been the same as the one called "Bielmiski (Antoine)" in Saint-Hilaire's Squadron Napoleon list.
Second, from register GR 20 YC 8 "1er régiment de grenadiers à pied, 1799-1814.28 septembre 1813-19 juin 1814 (matricules 3 321 à 3 900)":
Manuscript page 2 = digital version page 6: "N°. 3327, Conrad, Adam", with the comment "Parti le 7 avril 1814 au B[ataill]on de Lisle D'Elbe".
I couldn't find a "Conrad (Adam)" in any of Saint-Hilaire's company lists, though, so this would be an example of a soldier omitted from Saint-Hilaire's list (unless I've overlooked something) …