Gamestop has Gamecube Adapter for Wii U: $19.99 - Ships by 12/15 (Online Only)

Are we thinking these are going to see out quickly? Or would I be ok to wait until tomorrow (don't get paid until then, but I COULD order it now if I had to)?
Still gotta get a Wii U and Smash Bros first, however this is good atleast I know I'll be able to find one other than on something like playasia. 20 bucks is a good price.