Who should I trade for Eddie Lacy?

I think Lacy has a lot of upside when he comes back and that with GB being up a lot, he will see a lot of action against tired defenses in the second half. I need another strong back. Here is my team. Which should I trade for Lacy?

P. Manning- Not willing to trade
Vincent Jackson- WR
Julian Edelman- WR
Adrian Peterson- Not willing to trade
Knowshon Moreno- RB
Coby Fleener- TE
MJD- RB
James Jones- WR
Jordy Nelson- WR
Greg Olsen- TE
Michael Floyd- WR
BenJarvis Green Ellis- RB
Sam Bradford- QB
Bobby Rainy- RB
Phil Dawson- K
Chicago- Defense

TIA