The best option would obviously be the Pro Shop in the TD Banknorth Garden/North Station. If not, I would try City Sports (there's one in the Back Bay on Boylston street, at Downtown Crossing on Bromfield street, at BU on Comm Ave, at Chestnut Hill right off route 9, at Porter Square, and at Harvard Square on Brattle street.) Outside of the city I would try Moddell's or Dick's Sporting Goods. Hope that helps.