EDIT: Nvm, I see you're looking for the *new* 3DS, my bad. I would just wait until it gets released in the US, they'll probably have some on their site soon after that.
EDIT2: Alternatively, you can try to order some over the phone, you probably have a better chance that way.
Purchase Over the Phone
Nintendo of America Inc. offers convenient phone orders using a Visa or MasterCard.
For assistance, please call Nintendo's Customer Service Hotline at 1-800-255-3700 between the hours of 6 a.m. and 7 p.m. Pacific Time, 7 days a week.