I think opossums in general are a group that are much more common in private than in public. There are at least five species I know that are about in Europe (with another two being present in America) that are either very rare or absent in zoos, and when present in zoos they usually come from the private sector.
~Thylo
Can you elaborate on the Opossum species you mention here? For Europe would these be the same 5 listed on zootierliste? Then the additional 2 in America are Common Opossum and bare-tailed woolly opossum?