Currently, one does not exist. However, we have a few things in development at the moment because this has plagued me for quite some time. I'm also writing this post for other discussions to be directed to. So, let me pose a few things:
A complete VGA solution for portablizing would imply/require a constant, stable 480p signal. This is based on a little of what I've heard as well as what I've personally experienced. When the Wii outputs 240p, 480i, etc...basically anything that isn't 480p, the vast majority of screens I've used will not display video, only "No Support/Out of Range" or some variant. This is because most VGA monitors are expecting at least 480p or above.
How video is displayed is determined by whatever software it's running. For example, almost all homebrew supports 480p natively, as well as Wii games, VC games, etc...but not GameCube. This is why "Forcing Progressive" is such a big issue, and why one of the first changes we made to stock postLoader was adding the option to Force Progressive via args when booting games with Nintendont. This sometimes isn't as easy as flipping a switch, and while most games appear to support it, there are a few that don't. My personal favorite is MegaMan X Collection; which upon booting one of its games, always reverts video back to 240p, making it unplayable over VGA.
This means that in order to have a constant 480p signal, you need what's called a "line doubler." The details aren't overly important, but if you have one of these, it doesn't matter what the Wii is outputting, this'll deinterlace it and render a 480p signal. For Wii/GC, this is only available on GCVideo-DVI...which is HDMI, not VGA. Which brings us to the current status of additional video output options on the Wii.
1. Unseen has already come out with firmware for GCVideo-DVI to support the Wii. This'll at least net you HDMI, provided you can get it working. As someone who's wired it a few times....it's finicky and hard to get stable. Sometimes even when the picture is perfect, the OSD doesn't work correctly. It's not something I would recommend for portablizers at all, and of course, isn't VGA.
2. Then there's the analog GCVideo, the GCVideo-lite. Currently, with modifications to the firmware thanks to
@Aurelio, this is the only way to get non-converted VGA(ie not Wii2HDMI or external component to VGA converters.) The signal is pretty okay, but there are quite a few drawbacks. There's some weird native interference, that's
visible on some screens and
invisible on others, related to how the screen interprets the resolution horizontally, or something like that. It also possesses no space on the FPGA for an OSD or line-doubling feature, meaning that whatever resolution the Wii outputs is whatever you get.
Beyond all of this, there are the additional drawbacks of every idiot and their mother coming out with increasingly shittier board redesigns to try and corner the market without fixing any of the real issues. Granted, these are all for GameCube, where you can get away with being a total fuckup that can take shortcuts, but the Wii never intentionally supported digital out and the data signals are 1.8v instead of 3.3v, which appears to make them more sensitive to shitty board designs. This is also why despite mega having GCVideo boards available, I never released any of the GCVideo stuff I worked on and had previously mentioned in the MerWii Christmas thread. Instead, we've opted to work on our own, proper solution(s).
Anyways, tl:dr you're fucked if you want full compatibility. Otherwise, the most workable solution is CFW GCVideo-lite. Be glad it's not GCVideo-lite for N64, a console which basically has no 480p and requires line doubling. This is what makes the UVGA by
@marshallh so damn good though. Hopefully whatever we come up with will be similar to that.
