+1 on 11 year old post. However:
I paid $4-$5 for mine (36 mm) years ago when Sears was clearing out their sockets for ones with the size laser etched on them. I think that the original type has been brought back.
You're supposed to torque that nut, and to a fairly hefty value. You must have a very special adjustable if it reads torques.
The same socket fits the steering stem head nut. It's aluminum and also gets torqued so you don't want an adjustable there.