Personal Video player 4.3″ to 5″ screen size, what are the options?

Hello everyone,
My Ainol Media Player has a 4.3" screen size but the battery works incorrectly since I left the player running for extended hours. Now, I am looking for any device that will work best for watching videos only. Teclast and Ainol is no longer making such products so I am looking for a good alternative.
The player should be 4.3" to 5". I don't like bigger tabs as it is not very handy. Bigger screen mobile phone will do as long as it can be use as a video player. I am presently using an iPhone 4S for watching videos but I am not comfortable with the screen size, though it was fine. I am willing to spend dimes on buying new or second hand unit. Anyone have an idea?
