I've noticed, that it seems that all the automotive LCD screens are made for NTSC input. I haven't seen any that are actual "computer monitors". I wonder if any of the manufacturers of these devices are aware of the growing auto/puter community and might start making these.
Earth sells some 12 volt vga monitors at http://www.earthlcd.com/monhome.htm. A little pricey but that's probably the best you will find other than the xenarc. I have not seen any in-dash units that are vga.