As a newcome to this thread, I a bit late posting, but I would just like to comment on two points made by Remi.
1) While the official archive of the Bourbon-Parma family may still be in Lucca, the private archive was removed some years ago and its present whereabout are unknown. This was pointed out by Luisa Trebiliani in her "Studi Storici Lucchesi" (1992) on page 36: "si ignora la sorte dell'archivio privato dei Borboni, che per un certo periodo sembra sia stato conservato in una villa della campagne lucchese". This makes it totally impossible to carry out detailed research on the private life of the family.
2) Again, while by far the largest part of Enrico, conte de Bardi's collection is still in Venice, with perhaps a small part in the University of Padua, I believe that the Mussolini government returned a number of items to Japan in the years before WWII. None of this seems to have corresponded to Enrico's wishes. Following his death in 1906, Ca' Vendramin reverted to the Lucchesi Palli family, one of whose forebears had been the second husband of Carolina, Princess of Bourbon Two Sicilies and Duchess de Berry, the original owner of the palace, who had sold it to Enrico sometime in the 1860's. Enrico's widow seems to have wanted the entire collection removed to Schloss Brunsee in the Steiermark, which had become the Austrian home of the Lucchesi Palli, but WWI intervened and it was instead seized as a spoil of war by the Italian government at the end of hostilities, perhaps because Austria was regarded as an enemy nation. Whether any part of the collection reached Brunsee between Enrico's death and the outbreak of WWI is by no means clear, but Brunsee seems to have belonged to the Lucchesi Palli until at least the 1950's.