On ebay there is a section called "spares or repair" where usually there are several potable DVD players for sale.
The best ones to look for are the ones described as " sometimes works" They may not play DVDs but they make excellent
video monitors. I bought two of these players for less than £10 each both came with batteries chargers and carrying cases.
A word of caution, not all players have video in sockets. Before bidding download the user manual and check if there is an
A/V in socket on the side.
Good Luck