Per MLB Trade Rumors the following left handed relievers are free agents:
Name (Age)
Dana Eveland (29)
Pedro Feliciano (35) - $4.5MM club option
Mike Gonzalez (35)
Tom Gorzelanny (30)
J.P. Howell (28)
Rich Hill (32)
Will Ohman (35)
Manny Parra (30)
Rafael Perez (31)
J.C. Romero (37)
Daniel Schlereth (27)
Hisanori Takahashi (38)

Howell, Gorzelanny and Parra would be too expensive I'd guess.

I think the Reds best option may be trade Ondrusek or Arredondo and the salaries for a non arb lefty such as Donnie Veal of the White Sox or Jordan Norberto of the A's.