How are you determining that it has a significant bend? I'd think it would have been most obvious right when you picked it up at the LBS or before you put it into the hub.

The comment that you only noticed the bend after you installed it makes me wonder if you're seeing the usual (and normal) slight wobble of the freewheel which is unrelated to the straightness of the axle. It's been awhile since I had a bike with a solid axle, but I don't remember any problem getting a straight replacement when the one on my old Schwinn Varsity snapped.