why do you think you need a screenprotector?
for the record I have a 2nd hand 4-5 year old 40d, I dont use a camera bag (just throw it in a backpack), and it has no real scratches on it.
I wouldn't bother with a screen protector. (Reminds me.. I never understood how in previous years many nikon camera's shipped with the bulky screen protector by default. Thats like telling your consumer, hey.. the display is prone to scratches, but instead of fixing the display, we're gonna throw on this ugly piece of plastic. (-- sorry, Im a designer..this stuff frustrates me