For this, and masses of other uses, I went to my local newspaper office where each morning they put out the paper ends not used.
They sell them for 5 dollars or so, depending on how much is left on each roll. I got one that should last me the rest of my life but school teacher DD wanted it. I had to go and get myself another one, it is so good to use for a lot of other things and it's pure white so no ink messes.