Really easy way to find Guitar Hero 3 for the Wii. Every day, just go to another store and look for one. Repeat for several months. This is what I did to finally find a Wii.
In all seriousness, I finally got Guitar Hero 3 for the Wii. I had been looking for a Guitar Hero 3 while but just could not find one. Understandable since it was a hot gift for Christmas, but even several weeks after the fact, it was still kind of amusing to me that I couldn't find one. I wasn't looking hard, but I was looking. I would just casually look whenever I was in a store that might carry it like a Target or a Best Buy.
Today, I walked into my local Target, and there were three just sitting there. Was tempted to buy all three, and resell them for a profit, but decided it wasn't worth the hassle. Just got lucky finding one I guess, kind of like what happened with the Wii. Although I somehow doubt the game will still be impossible to find this time next year, unlike the Wii which is still pretty damn hard to find.