To be honest, I picked up the component cables for the original Wii back on launch day, when it launched in 2006. It was on sale for $9.99, but I had a friend who worked at the store, so I got it for $5 instead. Not a bad deal. So I stuck with that the entire time. Never needed the HMDI for the Wii. Nor did I need it for the Gamecube, as I just used the basic A/V cords for that.
I have a friend who is a real stickler for HD. Like, to a ridiculous degree. For instance, he had finally gotten himself an HD-TV, back when they were relatively new. And so he wanted everything to be in HD. And he had a 'Monster Cable' HDMI plug for his Playstation and Xbox. He got himself a Wii as well, but was furious when it only had Component Cables available, not an HDMI cable. He had open Component ports in his tv, but he wanted everything to be HDMI. He put up with it for a little bit, but eventually, he refused to play the Wii because it didn't have an available HDMI cord for it. It has converters and adapters and such now, but when it first launched, nope, it had nothing. Just Component.
My friend, tho, he went to a "ridiculous" degree with HD. For instance, if that wasn't enough to convince you. Here..... We used to have movie nights all of the time. Once a week, we'd get together and spend hours upon hours watching movies. We'd all bring our dvd's over, and we'd pick what we want to watch, and we'd just pop one in after another. This is before any of us bothered with Netflix, by the way. But anyways, after he got his HDTV set up, he refused to watch anything that wasn't HD. It seriously got to the point where he would happily go to movie night with us, but get upset when there were only dvd's, and no bluray's, which were still brand new at the time. So they were still expensive, and hardly had any movies on the format yet. But, in his new, snobbish ways, he would get upset, and refuse to watch DVD's because they were too "low quality", and he would leave. It's insane. Even to this day, he's like that.
Especially with games. If it doesn't have "realistic" graphics, he wont' touch it. All "cartoony" games, he refuses to touch. Like, The Legend of Zelda: The Wind Waker HD or the new Duck Tales: Remastered.. nope, he won't touch them, because to him, they "aren't HD". For him, it has to have as close to "photorealistic" graphics as currently possible, at any given point of the generation. Like I said, it's gotten to a ridiculous point with him.
Anyways, I could go on about him, but I won't. So, back to the HDMI cables for the Wii and Gamecube. Again, sorry, I have no first hand experience with any of those, so I can't give you any real advice on those. My friend, who is an HD nut, doesn't even have one for either. I don't have one, he doesn't have one, and nobody I know has one. Everybody I know still uses either the standard A/V cords, or Component cables, for those systems. Nobody I know uses HDMI for the Wii or Gamecube. And I have no plans on upgrading my systems to an HDMI cord for those.
So, sorry that I can't be of help. I can try to look up some reviews for you, of random converters or adapters, and what not. Can't guarantee that I'll find anything worth your while. But I'm sure that there is something out there, somewhere, that people like. In the meantime, good luck with that. Hope you find something that works, and that you like. Good luck again.