I have the exact same netbook, and I've been searching for the answer to that question myself. Are you certain that you can't add this slot? The soldering may be extremely difficult, but it appears possible... since there is a spot for it:
Just no RAM clip/holder/etc, to put the chip into. I also noticed CPU-Z shows "Slot #2" in the dropdown. But I wonder if it would even be recognized by the bios, since it was clearly designed to use a maximum of 4GB.