Capture Card for MacBook Pro running OSX Lion?

Hello,

I'm planning on starting a LP (Let's Play) in a couple weeks for Skyward Sword and realised that I really need a Capture Card to get the best quality, but pretty much most of the ones online are only compatible with PCs and the ones which are compatible with Macs either give really crap quality or they're really expencive.

Does anyone know an affordable capture card that I can buy online that it compatible with OSX 7.1, gives good quality and is able to record from the Nintendo Wii?

Cheers

Leon