Wii U GamePads - replacements can be ordered through Nintendo Consumer Service

Wii U GamePads won't be sold separately in the US due to Nintendo not wanting any consumer confusion to ensue, however, should you break your lovely new second screen controller, you can order a new one. Just be aware it will cost you, and Nintendo isn't saying how much - yet.

Replacement GamePads can be ordered through Nintendo Consumer Service, while a stand-alone controller will be sold in Japan for ¥13,400/$172, how much one will run you in the US should it get broken or damages will be revealed by Nintendo "closer to the console's launch,"
the firm told Polygon.

In the west, Nintendo's product marketing manager Bill Trinen
said over the weekend that consumers will be able to purchase the GamePad singularly when there are games released to support two at a time.