The lenovo thinkpad x-series is a contender, it's really small, but I don't know if any are available under $1k. I'll pm you a place to check. I'm guessing apple will be coming out with a smaller notebook next tuesday, but it will most definitely be over $1k. Fujitsu makes a lot of super small notebooks, as does sony. But the super small notebook is aimed at executives, so most of them are pricey.
If used or refurbished is ok, check for mac powerbook g4 12", thinkpad X series, sony ux series. The UX is probably too small for major writing unless you use an external keyboard and display.