I don't think Celeron M CPUs have advanced power management instructions like Speed Step which makes them cheaper to manufacture.
I think Intel disable SpeedStep in CM just to make PM more attractive, it's not a question of manufacturing cost.
UNDERVOLT IT! It's your only hope. I don't know if it's possible with your laptop, but you should really try. Since it's only running at 1.4 GHz you can possibly lower the Vcore pretty much.
Since it dosen't use SpeedStep you can also try a pin mod if software won't allow undervolting. Check Intel Datasheets
, page 15.