I bought this one:
Console Plus: PlayStation 2 » AV Cables and Adapters » Universal AV/Svideo 3-in-1 Cable
However, I just realised something...the composite cable I use
isn't the one that came with the N64, it's the one that came with my GameCube. So that's why I see no brightness difference in the images. There are two possibilities:
1) Both cables are too bright because they lack the resistors and capacitors
2) Both cables are fine because the N64 has the resistors and capacitors built-in
I've never heard of option 2 so I assume option 1 is correct but then, as you can see, it looks fine so if it is too bright, the difference must be smaller that other people seem to experience. The way to know for sure would be to compare it with the original RF cable but I have no idea where I put that.
I kinda want to try soldering the correct resistors and capacitors in the cable connector at work to see if I get an "aaah that's what they mean by too bright" moment but then it might be so close to normal now that the extra resistors and capacitors will make it too dark, which'll ruin that S-Video cable. :/