You may find it difficult to obtain a replacement LCD and if you do it will probably cost as much as a new TV.
However if you wish to try, take the back off the TV, on the back of the screen there should be a number stamped. This is the part number for the screen.
Go online and enter just this number in the search box of your browser, do not add Sharp or TV to the search term. It will just skew the results. You will find that the screen will most probably have been made by a manufacturer that specializes in screens and not Sharp. Good luck!