If you want to talk about a center who might not cost us, oh I don't know, the second best player currently on our team, but who might work as a decent defensive starter, how about Bismack Biyombo? He's stuck behind Al Jefferson for the foreseeable future, so he might not cost that much in a trade.
He doesn't have much of an offensive game, but he rebounds and blocks shots. Plus, plenty of upside still.