Why not create a global chat channel called "lobbyListeners".
Then - when a user is viewing the lobbies - have them connect to and listen to the lobbyListeners channel.
Then you don't need to maintain a global entity at all. Whenever you create a lobby or delete it - send an event to lobbyListeners - and it will automatically send it to everyone who has registered for the channel.
Would that work? (or is there a part of your use case that I am missing?)