VGA -> NTSC
Try Vine Micros in the UK +44 (0)1843 225714 (fax 296 237). They have a device
called the MultiGen which does this at up to 640 x 480 x 24bit. They also do
various other bits and pieces which you may find handy.
They have a distributor in the US – don't quite know who.
Tell them Jason told you about them.