If you have the prism for it and you just need a lens mount attachment at sensor distance from the prism and two reverse mounts on the other side of it to mount

If you have the prism for it and you just need a lens mount attachment at sensor distance from the prism and two reverse mounts on the other side of it to mount mirrorless cameras on (assuming light comes out of the prism straight or if you can just split the distance between each side of the prism -- note I have no idea about this) it doesn't seem that expensive - buy a couple mirrorless cameras, get yourself a cube with the mounts, and get going with one lens, no? It seems like the cube with mounts is the most expensive part, and there's no way it can cost more than one of your cameras, let alone the lens, right?