Hello RialtaMan and welcome,
Some of the items should be an easy find; new or used like the sink and the stove. Someone on this site had the QD second row seats for sale a while back. Not sure if they still have them? As for the bath setup, what are you missing? Did someone take everything out? If it is just some misc. parts they could still be had from Winnebago in some cases. It would be rare that anyone would take this apart, however, I did get a replacement Generator from a wrecked Rialta that was in New York. You could try to find such a case and remove the bath system as I doubt anyone would think of that if they had a wreck sitting around. Keep posting and let us all know. I keep encouraging people to write more stuff on here. I am just one of the members but hope to see more activity so we can all help one another. btw: I have a 1999 HD.