Firstly, just to prove it is the scre that is at fault, have you got another screen you can "borrow" for a couple of minutes just to try out. That will isolate the fault to the screen or something else in the chain.
Secondly, the price of screens is dropping all the time, with a 17" CRT now available for under GBP70, and a 17"TFT screen for under GBP170, so if you can't fix it as described above it shouldn't break the bank to get another.