See CosplayMagic at the related link below .
Anime conventions are your best bet for cosplay. That or Harajuku Japan.
If you need a cosplay fast and cheap the best place to always go is the thrift store that's where I have gotten all of my cosplay. (And I cosplay S. Italy)
The best place is to get one is on Amazon.com. If you are trying to cosplay, then you can find one there.
well, my friends bought few costume from there and said there the best out of all the cosplay costume site, and I also heard that cosplayhouse.com is u.s based store
TCS Presents - 2012 WonderCon Cosplay Best Cosplay 2013 Edition 2-1 was released on: USA: 4 April 2013
TCS Presents - 2012 Comikaze Cosplay Best Cosplay 2013 Edition 2-4 was released on: USA: 7 November 2013
TCS Presents - 2012 Comic-Con Cosplay Best Cosplay 2013 Edition 2-3 was released on: USA: 23 July 2013
TCS Presents - 2012 Comikaze Cosplay Best Cosplay 2012 Edition Part 1 1-3 was released on: USA: 2 October 2012
TCS Presents - 2012 Comikaze Cosplay Best Cosplay 2012 Edition Part 2 1-4 was released on: USA: 2 October 2012
There aren't any specific "Naruto" cosplay shops. Most carry all different costumes. The best one's happen to be online stores and the best online cosplay store happens to be in the links below :)
Ebay is a great place to look for Cosplay props. There are also numerous websites which sell similar cosplay props. Your best bet would be using Google and typing "Keyblade prop" or something along those lines into your search.
Most likely Matsumoto-Fukutachou (Vice Captain Rangiku).