I actually got myself 3 extra sets less than a week from launch. Target had just gotten a shipment in when we went by there. We lucked out.
When I got a Wii for my mother though, no such luck in finding extra remotes. Luckily, and I say this now, one of my controllers wrist straps broke resulting in a flying controller. It still works, but the rumble is now audible. When we called Nintendo about it, they decided to send out another remote for us, as well as a fixed strap. Since I already have 4 controllers, I am probably just giving my mom the second controller as well.
With that said: I have seen them around in Portland, Oregon. It just depends on how much you check, and how diversely you check. Checking one store doesn't necessarily get you anywhere.