BMW e38 video, RGsB question

Hi gang, newbi here... I did some searching on this topic and go close so I thought I would ask....

I'm looking to add an external video source to my 2001 e38 7series. It's the widescreen MKIII version. It has RGsB inputs and I'm looking to build a converter from composite to RGsB to feed it.

I know that converters exist but I'd like to build a variation that gives me flexability and reduced cost vs. something likethe navtool device.

anyone got any good plans or schematics to do the composite to RGsB conversion?

Thanks,

todd