A word of caution: check the voltage. We use a lower-voltage model than the original, which saves electricity, but can contribute to slower battery charging, say, if that's important to you.
Also, if you want to keep it local, you may want to talk to Ardi at Fixatronix on South Street: http://www.fixatronix.com/
or try the apple store on Boylston Street in Back Bay.