Arent memory cards for wii and game cube the same? My Game Cube Memory card fits in my wii at least.

You'll be able to get a GC card that's branded for Wii, but they have a pitiful capacity. Best bet is a Datel or Nyko one - they're the only companies still making large capacity ones, although the 128 meg one is pointless. Why?..

Well although you could technically fill the card - it's not actually possible! The GC has a hardware limit of 127 files per card, and even modded consoles (like mine) can't get past it. At most you'll half fill a 128. :s
Anywhere that sells Action Replay tat will be able to order a Datel card, get the 64meg - it'll cost roughly Ѓ7.

Skulfuk said it will be about 7 euros. According to the top currency converter on google's list that is just over $14 AUD

I would donate one, but mine have all been doctored due to the amount of multi-region saves I have.

E-bay's still your best bet.