Judging by what is on my print drier, you'll want about 7 to 10 oz. cotton canvas. 12 oz. will probably be too heavy. Luckily, light/medium weight canvas like this is easily obtained at any art supply shop. It's the cheap stuff when it comes to stretching canvas for oil paintings. Linen is a
lot more expensive, as is the heavy "wagon cover" canvas that is necessary for large paintings or floor cloths. The trick will be to seam the edges very neatly so they don't take up too much of your drying area.
Here is the
Dick Blick reference, but you can probably get a smaller roll or blanket at a local shop. Try any hobby painter, or one who works on small paintings, one who stretches his own canvases. He or she will probably have scraps and give you some.