its gonna cost you about 300 dollars, i would just get yourself a formac monitor, it will work natively and it still looks appealing to the eye with its similarities to the apple display.
You can order directly from their site, or from any of the major Mac mail order places. If you already have a nice Cinema Display, then it may be worth it, but the quality isn't as good as using a DVI to ADC adapter. However, I have used this and it works well.
If you don't yet have a PowerBook, you may want the 15" or wait for the 12" to get a DVI port (who knows when that might happen?). If you don't have the monitor either, then you can always get a flat panel screen with both VGA and DVI inputs. That way you can still get the 12", which as you know is a sweet computer!