I looked through my old links and didn't find much of anything useful, just that the D-Sub has three extra wires attached to the back of the PCB. You can desolder those and use (two of) them for your H and V sync signals. The process is otherwise identical between the two cables, D-sub is just easier because you don't have to add extra wires. I don't think there is a way to get a d-sub cable at a good price, unlesss you know someone going overseas.
There's a third option, which is to take Nintendo's cable off the PCB alltogether and solder a VGA cable to it directly. If you go that route you won't have to pay extra for the D-sub cable, but the soldering is a little trickier (and you'll need to find/buy a good VGA cable).
Tell me if you're interested, otherwise I don't want to get too wordy about it.
Good luck in any case.