Schluter Products offer a full line of tile installation products including this easy to install shampoo niche. The unit comes waterproof and ready to install. Fits anywhere with a 16″ space which is industry standard for framing. More info can be found at www.Schluter.com.
You can also add an additional layer of water protection using Ceramic Tile Pro Super Grout Additive™ with sanded cement based grout such as Polyblend found at Home Depot or Mapie Keracolor at Lowes.
More info on Super Grout Additive™
TheGroutStore – official supplier of Ceramic Tile Pro Super Grout Additive® and Ceramic Tile Pro products
YouTube – officially supported how to videos using Super Grout Additive™ products by TheGroutStore.com
Amazon – original genuine grout repair products manufactured by TheGroutStore