If you don't find what you're looking for at a print shop, try an office supply store.
They won't have 'full folds', but can supply you with pads of the type of paper you're looking for in a smaller dimension. That kind of paper is called, 'newsprint'. They might not know it by name.
If you're mailing small, article-like pieces and attaching them to a larger piece, you'll increase your response if you cut the edges with a jagged scissor called pinking shears. No, I don't know why that works.
Also, you can sometimes get away with photo-copying a piece of 'goldenrod' (yellow orange color) paper. That will render the right color,
sometimes. Then, write your article on the copied, now correctly colored piece of paper, then copy that.
Peter