Bricks (and stones, and other architectural textures) are a common scenery dilemma. There is hardboard that can be bought with a variety of patterns (often even available at the local lumber company), there are vacuum form panels, you can cut them out of foam (rout them out then go over with a heat gun, you can cut grooves in the foam with a heat knife) or you can cut out a billion squares out of a variety of materials and then shape them, then apply to a substrate (of which homosote give a nice, but very messy effect). What would be interesting would be a side by side comparison with a variety of different methods, all covered with a similar paint treatment. Of course the issue here is that just as there are a hundred ways to cut out the bricks there are another 100 ways to seal / and paint it (foam coat, sculpt or coat, super 88, flex glue, and so forth).
Below are a few links with a variety of brick options. It is not an exhaustive list by any means, but a few sites that I have located in my current search to find flexible bricks that would hold up in an environment filled with water and little kids.
In case you would like to build your own vacuum form table.