I have absolutely no idea how one would create this for a reasonable sum of $$$ but I had a student with decent 3D modeling skills rough out my design.
each 'cell' is a 1" square 6" tall... with a 3/4" square tube in the center...
that's 24 square inches per cell.. with 36 cells... that's
864 square inches of HHO production by my rough calcs.. seems like it could generate a lot...efficiently? I dunno...just something I dreamed up...