Probably the most difficult species of Drupa to get is Drupa elegans from
Polynesia.  Drupa iodostoma, also from Polynesia, is also uncommon, and seldom
available (this one is often described as a subspecies of Drupa morum, but it
is quite different in appearance).  Drupa clathrata is uncommon, but not as
uncommon as the two above, and more wide-ranging.  The rest of them I would
say range from fairly common to abundant.  The commonest ones, in my opinion,
are D. morum, D. ricinus, and D. grossularia.
Paul M.