You usually won't be able to find patterns for purchase that are specific to cosplay. Most people either end up finding a clothing pattern that is similar to what they need to make, and modifying it. Or they draft their own pattern.
Yes, there is Rei Ayanami cosplay patterns for school uniform - acparadise.com/acp/display.php?c=50214
Ebay
Try the related link below for Tsunade pattern ideas .
I know cosplay locator makes crazy custom stuff like that. But be prepared to pay out the wazoo.
Anywhere, any time! It's best if you go to Cons though, or cosplay with a group of friends, it makes it more fun.
The company at the link below makes custom cosplays.
It is basically an interview that describes your cosplay. they have questions that you answer such as , What got you into cosplay? How did you decide on this cosplay? How did you put together this cosplay? Basically a self interview on cosplay.
For my Ciel dress I just altered a Butterick pattern found at your local fabric store or Hobby Lobby.
buy? gee, well he's a hard dude to cosplay. the cosplay.com marketplace might have one for sale. you could always make one, which is just looking at what others have done for repliku/dark riku and changing the colors and patterns
Try the cosplay suggestorator..
you can buy a cosplay costume online or you can make a costume yourself. There are also many places where you and other people can cosplay known as cosplay events.
You can cosplay any character! cloud-terra .com has some awesome outfits for cosplay!