RE: Water Tank.
Go to Ebay and, in the search box, type “HO Water Tank”. You’ll see a number of water tanks ranging in quality from toy level to high caliber. Some are listed at bargain prices.
Look at the yellow model power tank (which is listed as of this post). It looks reasonbly close, in appearance, to the Tyco version used in the “Petticoat Junction set” set that I posted about earlier. [;)]