Tate,
The previous owner of my boat had a really good unit (forgive me for forgetting the brand) that he had mounted on the bathroom sink. Yes, I know, an eyesor but maybe it can lead you to some ideas, it was plumbed to the seacock in the bilge near the starboard pullout setee close to the mast and the brine discharge was the head sink drain.
I could contact him to see if he would dig it out of his storage and sell it.
I believe it to be a good unit that kept the tanks full.
I did see it before I singned the papers for the boat.
Carl