You can find the Infamous costume on little big planet in the store, but if it is not there anymore your chance to buy it is gone.
Go to the stores and buy one with money you earn from completing islands
Costume shop
There are plenty of Riddle Costume for all ages that you can buy at many halloween costume stores.
Its an awesome costume you should buy it. Yes, if you like the costume, you should buy it.
Yeah, they are not bad. You can always find good coupon on their site. And most of costume are cheap, so not a big risk.
Hey, You can buy one @ display and costume or party city.
You can make an easy homemade one like I am. I tried it before it was fun!
As of 2014, the best place to buy a Sora costume is at local Halloween and costume shops. This costume may also be available at some anime and comic stores.
Costume shop in your local area or if not on ebay
One can buy a bear costume at many costume shops online as well as in Shopping areas. Popular ones are Party City, Target, Amazon, and Professional Costume Mascots.
It is likely as not going to be released as a DLC, to milk more money out of the consumers.