My experience is the USB powered drives are slower as they cannot draw enough power from the USB port to spin them at the faster speeds. If speed is not an issue, then by all means, get one.
That said, there are a large variety of external drives. You could probably go to a local store and find one as well.
As long as it is a DVD reader, it will most likely be able to read CD's as well. You won't need a BluRay reader. Just DVD.
I like Samsung and LG.
http://www.amazon.com/LG-Electronics-Portable-External-GP65NB60/dp/B00ODDE33U/ref=dp_ob_title_ce
