To the best of my knowledge they aren't really that many alternatives and I don't think any of them do a great job. I know a lot of people here have bought many gadgets but I remember a lot of frustration and comparisons to how well the Dreamcast played over VGA, so I'd assume you're not gonna have much luck.
Have you tried connecting through a component cable?
PS2 games still don't look that good upscaled on the PS3, so I'd assume something along the lines of what you're looking for isn't going to do a job to the standard you want.