Bike Bits shopping in USA?

I'm on a whirlwind visit into New York (staying on 6th Avenue, between W53rd St and W54th St) for a few days - Monday to Thursday next week.

I'm wondering if there are any decent bike stores walking distance from where I am that might be worth a look in to buy some equipment cheaper than what I can get it for here in Australia (particularlly after road equipment like rear cassettes, chains, tools, etc).

Any hints would be good as i'm not going to have a lot of time, and want to visit some other places (MoMA, ground zero and such). Web sites would be good too.