North Carolina and San Diego Safari Park, both in very large enclosures. I can only think of Prague in Europe.
At Safaripark Beekse Bergen in the Netherlands Sitatungas are kept together with Nilelechwes and also Common hippos are kept in the same enclosure. There are several pictures of the animals and the enclosure at the Safaripark Beekse Bergen Gallery.
Prague keeps a bachelor group of sitatungas sometimes together with a lone male of lechwe and/or megaceros.