What exactly do you want to buy? Is it a carbon pen or a carbon rod or a carbon strip?
Charcoal can be painted on canvas. Of course, just like pencils and charcoal pens, if the canvas refers to linen, you can sketch on the canvas with charcoal pen or without a brush. If you want it to be strong, you need to spray Spray Fixative.
There is only one kind of colored carbon rod in China, which is actually reddish brown and relatively hard, and is suitable for sketching on rough paper. Flowers in the art museum, Xueqin in Haidian and Shazikou are sold in many art shops, three in a box.
If you buy colored chalk, go to these places too. There can be more colors. Colored chalk is softer and easier to use than carbon rods.
Brown red and brown charcoal chalk commonly used by westerners are not sold in China, nor are colored charcoal pencils sold in China.
That's all the soft materials for color sketch. You can buy it at your discretion. However, the domestic brown carbon rod is hard and difficult to use. It is difficult to draw on canvas, so you can only draw on paper.