You can check out the 4 different colour options at Amazon Japan. There are two Famicom styles in red and gold and also two more contemporary Wii styles in white. They will retail at slightly less than a classic controller at 1,659 Yen which is around $15 USD / €10 / £8.
There is no news on these being sold outside of Japan so importing might be the only option. They will be available from 10th September. If we see these pop up on Play-Asia we’ll let you guys know, otherwise Amazon looks like the place to go!
Source: Amazon Japan