Hallo!
there can be design with container, i will suggest to use plexiglass. draw a blueprint with all needed pieces in needed sizes and go to 'adwertissement materials' workshop, where plexiglass will be cutted in your's specified sizes. later you can glue them togeather using dihlorethane (CH2CL2)
but also there can be design that did not use any casing at all
there is container from 8mm thick plexiglas, and assambled with stainless steel plates, can be seen in attachments. also, with distancers from white eraser rubber
it has 10 cellls, and 3 steel plates in each cell, but if you want to make separated cells, it will be better consider how much cells will work most effective, to get 1,47V on each cell. there are great importance of electrolyte density (i used KOH with destilled water) the more gap - the more must be density. also, if electrolyzer draws too much Amperes, than electrolyte can bee made poorer.
but this design has some problems - low efficiency because not all of surfaces are used. and dangerous risk of little electric spark, between connectors and plates, it is not safe left electric connections abowe water line, or if, they must be solid and welded, so no spark can happen.
there in pictures you can see exploded bubbler, this was made from plexiglass, it exploded because of too weak gass flow through the torch nozzle, so, flame speed excess gas flow speed, and get into torch, where it heat bronze wool, and some seconds later, heat gets through bronze wool, and bang, there goes shivers of bubbler
last two files are about computer atx power supply, that can be used for electrolysis, because psu have 12V dc, and about 30Amps if two of 12V lines joined togeather (simply take all yellow wires as (+) and all black wires as (-) ground) there will be instruction how to correctly power on atx psu.
the effectiveness in this case, can be wery good if made properly. but there was some faults with my setup, lack of ampere meter and so on...
i am sorry for ruining your reading pleasure with my bad english...