Capcom was coy on how it will be made available, but you will be able to use it in February.
The additional Circle Pad will be available for use in Capcom's Resident Evil: Revelations, coming out on February 7, 2012, according to Capcom's Ryan McDougall at New York Comic Con.
McDougall did not say whether the second Circle Pad is coming out separately or in a bundle, but he confirmed that, if you want it, you will be able to get it.
We've known that the second Circle Pad is coming to North America, but we haven't had any hard confirmation of when it was coming. It will be out in Japan alongside Monster Hunter 3G in December.