Help for the Ignorant

My laptop needs a new battery. Specifically, my Sony VAIO PCG-V505BX needs a battery that apparently costs $140 plus shipping and handling if I order it from Sony. I'd like to see if I can't get it cheaper elsewhere. So I turn to you all for advice: who is a reliable retailer to get a Sony laptop battery from, other than Sony? Also, the laptop is now going on three years old, so I'm having trouble finding batteries for it at, say, Circuit City.com or the like.