The Canadian tire and depo ones will definitely work but you’ll find a much better brick from a masonry supply store. If your looking at doing an entire arch then I think you’ll be surprised at the cost. A masonry shop will also be Way denser and usually thicker. I bought a couple new pans from a guy on Kijiji that makes ss pans and really nice arches and pretty much anything to do with syrup production. He is in the Hanover area just for anybody reading. He was more then happy to sell me fire bricks at a great price as he gets them by the skid. Pretty much the only way to get them on the cheap if your doing an entire arch. Just an idea you could try if you have anybody in your area making them.
I use to work at a steel mill doing refractory Brick work on ladles and furnaces to hold molten steel. The ceramic fibre material might be hard to find at stores as it contains all kinds of bad stuff you don’t want to be breathing in and easily is airborne by just touching it or bending it. We use to keep it in a totally separate area when I was at the plant. I’m betting it’s our safety standards in Canada stopping you from seeing it at home depo.ca if you do find some what ever you do put a mask on when working with it and not just a covid mask lol.