I don't know any particular place, I don't even remember the place I had gone to honestly. I do remember it was in Michigan though, which turned out to be the best combination of brick price and shipping. All together I bought 4 bricks for about $30. Although there is always this not the cheapest but pretty much what you need to do what I did.
I have toyed with this idea too, but I think a better option would be to make a larger forge with fire bricks like this one:
and make a frame out of angle iron or whatever to keep all the bricks together and secure the torch in position.
I bought these fire bricks on amazon and put a thin layer of furnace cement around the inside and the front face just so I wouldn't scrape away at the brick too much (it's very soft and brittle.)
The heat source is a TS8000 torch. It seems to have at least enough to power a forge of this size (the inside is 2-1/2" in diameter.)