Audiovox DVD1680 7-Inch Portable DVD Player
Superlative quality for a reasonable price.
I purchased the DVD 1680 after a rather exhaustive search for a portable DVD player.  I took it on a business trip to Scotland, and it played superbly.  No problems chaging the battery from 240 volts British electricity.  I purchased an extra battery, and still had power left after 7 hours of use on the transatlantic flight home.  Beware of purchasing DVDs overseas - they will not work.  Even though it is PAL and NTSC compatible, there are different versions of DVDs recorded overseas this player will not read.