Need more info...
Do you need it to be a touch screen?
Do you need sun light readability?
Do you need vga, dvi, hdmi, or composite inputs?
Do you need a back up camera trigger?
What are you willing to spend?
High end "good" LCDs can be in excess of $700 depending on your needs. Average LCDs that are good for most people on here are $200-$300 or so.