Actually I have a spare one that I'd gladly sell you for less than what Apple will charge you. It was for my Powerbook 1.25. It was an extra. When Apple replaced them for free during the exploding battery bonanza, I had just bought a brand new one because my first one stopped working. So I got a brand new one for free to replace the dead one I had already bought a new one a month prior. I just sold my Powerbook to my friend, and she didn't want the extra battery so I am left with one I can't use on my new MacBook Pro. I think I used it all of 4 or 5 times so its essentially new.
So… if you haven't replaced yours, PM me and we can work something out.