Eww scraping I just bought a little squirt But if you must make one, it consists of a hose from the wall to the toilet with a connector piece for the little squirt at the toilet end. Another hose from the connect piece to the sprayer and the sprayer. It's a basic spray nozzle like what comes with a hose but only has one setting.

There are other nappy sprayers that are cheaper than the little squirt if you shop around.