I have an Air Boss shoulder bag that I usually take as my one carry on:
http://www.redoxx.com/air-boss/91018/product
It will definitely fit in the CR9 and CR7 overheads, except for the really small ones above the first class A side seats. I don't know if it would fit in CR2, haven't flown one of those in a long time.
I have also been able to fit a small and not overstuffed rollaboard on the CR7 in the past.