There isn't much available right now. Not much in the FA this summer, so unless some one wants out of a team, Zizic and Yabu will have to do until 2018 where there are two guys who could be top bigs in the league.
I'd be fine with a Dennis Rodman style player, some one who defends a high level, rebounds, passes well, and can actually shoot an out side shot even thought he didn't take many, but keeps the D from cheating off of him.