That doesn't actually mean the Stalker's screwed, though. Kon managed to grow his own soul. That's obviously a very different thing than starting with a soul and selling it off - just because you grow armpit hair once in adolescence doesn't mean it'll grow back again after you get it all lasered off, and there's no reason to think souls aren't similar, based on Stalker's history - but it does at least prove that "take an existing one" isn't the only solution.