Uhhh lower Arm is just a peice of steel with a ball joint in one end and a couple bushings in the other. Short of being cracked I see no reason why you need a whole A Arm. You can get the Ball joints and bushings at Aurtozone. Looking on
www.AutoZone.com site they do sell a over sized lower ball joint if the hole has been wallowed out. $17 . The bushings are $7 each (need 4 per side).
Advance is the same prices but the also offer a shaft kit that has bushings and the part that bolts to the saddle for $49. The also offer one that looks like is for a lowered truck that has more camber in it for $54.
Ahh under ball joints it shows a lower control arm for $100 and my guess is it includes ball joint and the bushings as well as the arm to deal with a wallowed out hole for the ball joint.
http://www.advanceautoparts.com
http://www.napaonline.com/ is about hte same for the off brand stuff.