they leave classical music on the radio on, turned down nice and quiet to calm them down. Also, use Rescue Remedy- but that's for anxiety and he's anxious cuz he's lonely. so it would be best I think to address the loneliness....
what about getting a gerbil? You wouldn't have to tell the manager...there would be instant entertainment... leave freshly grown catnip down (just a bit- dont want him to build up a psychological resistance, videos with birds and squirrels, cds with birds and squirrels, (i know these things only last an hour or so...). what about asking a friend to stop by once a day to visit him?
A pet sitter would charge way too much but a friend might just charge you an occasional lunch out? Does he have the mice with rabbit fur on them (I know we're not supposed to buy them but cats love them!). Ask Catmandu what he does for toys- he makes them and others on pettalk say they are very popular with their cats- worth a try! Good luck!