Good advice from it'sbeenawhile - I'd do the same. Mantei seems to be doing well on his way to recovery, but what will happen in the end is pretty murky at this point, although I expect the job will remain Kim's when the smoke settles.
As for closers who might be on waivers, you're probably limited to two choices:
a) Closers who are coming back from injuries (Leskanic, Gordon, Zimmerman).
b) Guys who might inherit the closer's role if their team's current closer is injured or traded. This is entirely a guessing game, but I'd keep my eye on Tampa Bay and Pittsburgh.
Oh yes: T.J. Tucker might be worth a pickup if you have the roster space; and if you're a real gambler, there's always Shaw...
If all those are available in your league, I'd grab Tucker, and when it becomes clear he hasn't become the primary closer, go for Leskanic.