big chart paper?

I think you may be refering to what we call "graph paper," which is paper with a preprinted grid. This grid is usually in a pale blue color so that, while visible, does not detract from the images placed on the paper.

Most office supply stores sell it, in sizes ranging from standard letter size, up to eighteen by twenty-four inch tablets. You can sometimes find these in flip chart pads, and, on desk blotter pads.

Check with the staff at an office supply or stationery store.

I would try an Engineering or Drafting supply company. They usually have products like that. Sometimes they also have art supplies as well. But I would call first. True art supply stores do not carry a lot of variety in graph paper.

Note; You mentioned A-4. I am not sure where you are but thats a metric size that is not commonly recognized in the U.S. But I am sure wherever you are there are stores that cater to the engineers.

Good luck,

Well, in Tennessee we have a great art supply store called Jerry's artarama that sells paper like that. They have a website.

Depending on where you are in the US, I'd try a university art supply store. If it's anything like the University of Tennessee, they'll have a whole store devoted to the art department where you can find that.

go to Staples and ask. or look online