Guys! @Fleder is correct. You don't need to buy a new screen. It just needs an adjustment to the overscan settings. You can fix/adjust this within the /boot/config.txt file to change this. You will need to hook up a USB keyboard to your PI or SSH in from another computer if you have Wifi setup.
If you are doing it from the GBZ, boot it up and then quit Emulation Station, and Really Quit and get to the Command Prompt.
Otherwise, from another computer, you can type this from a terminal (Use Putty if you are on PC)
The default password is "raspberry".
Now type the following
There you will see a text editor. Scroll down about 10 lines and remove the "#" character in front of the line that says:
Then press CTRL+X to exit, and "Y" to confirm your changes of the file.
Then reboot by typing:
If the screen still doesn't look right, just repeat this process, but adjust that number 16, until your screen looks right.