As a general answer - There were companies that offered pre-made bunk houses etc but most were made in the company shops by whatever railroad.
As for the shower car - If you want dimensions for modeling the late Ron Harr had an article either in an 80's Gazette of a mid 80's Timberbeast (the latter I'm pretty sure) I'll have to see if I can find it.
Also the late George Cummings oversaw production of 1/87 models of several Baker White Pine cars in Raul Martin (NWSL) Connoisseur Line although, not the shower car.
Lon Wall
Trainmaster Sumpter Valley Railroad