They're not hard to make. But a dremel rotary tool goes a long way. they're are several different designs out there, some easier than others. I used a 1" pvc
pipe with a dremeled down 2" to 1" reducer to act as the support (dremmeled to allow maximum water flow) for the 2" coupling. The other end (top end) of the coupling has another 2" to 1" reducer which then allows a 1" plug to slip into it. The plug was then drilled with a few small holes for air intake.