@sebbe67: I saw several pictures of the Liberian zoo, teeming with bushbucks and various species of duikers. Absolutely incredible! I heard that a conservation group has taken over, but couldn't find out much else so far.
I do think that US and European zoos might be interested in duikers; especially in the US, the breeding of several species has been quite successful, and more and more duikers appear also in European zoos. Leipzig Zoo even announced getting Zebra duikers for its new "Gondwana" project.
The main reason beside the political instability might be national epizoonotic regulations; Africa is still a dangerous source of several animal diseases that are threatening in terms of economical & human health aspects. Therefore many zoos are afraid about the red tape that awaits them when trying to get African wild animals, especially ungulates.