Ah I didn't realize you were planning an indoor system. I'd always thought you were going for one in your garden that is partially buried.
In that case, a prefilter will be less needed as you will have much reduced algae growth and foreign bodies entering the system. Do consider enhancing the ventilation for the area where the pond will be in however as you will get a LOT of humidity that can cause complications with your household appliances and furniture. Extractor fans will help much.
The cheapest way to get a bakki shower done is to build it yourself.
The trays can be made using stacking plastic trays like those from
UTOC, a local company.
http://www.utoc.sg/index.php/plastic-crates-basket/
If you want something nice made out of stainless steel, I think Max Koi Farm has contacts to get a bakki made to Momotaro specifications.
I personally think that a Zakki lantern shower filled with MarinePure spheres will work best for an indoor system. The even water distribution means you don't need the multiple trays and height of a traditional bakki.