Rv Shower Stall Looking For Rv Bathroom Parts. Anyone Have Good Sources?

Looking for rv bathroom parts. Anyone have good sources? - rv shower stall

I have a horse trailer with a small house that I would build. We already have a generator, air conditioning and heating, and we know where they get everything, but the material bathroom. We want one of those units, bathroom and shower combination. I saw the trailer in many sales. Unfortunately I can not find anywhere where parts sold. Those I have seen a very sharp angle corner with the whole space in the trailer, with a toilet in the shower. I think it is a holding tank under the form. Does anybody know where I can find them and what it costs about? Thank you:)