I bought a PVC check valve from a local hardware store for the basic dome shape.
I'm actually very pleased with the way it looks and the size. It's perfect!
I cut a part of the top off and sanded down some of a lip that went around the middle of the valve.
Then I wipped out the ol' dremel and sanded down the line-things on the bottom part, sanded down some lettering on the top part, and sanded a bit more on the outer ring.
Notice the perfect shape and size compared to the reference picture a the top.
Somehow, I menaged to completely gut the check valve, so now it's cmpletely hollow on the inside (that's a good thing).
Then I rigged myself a little device with more PVC scraps for the middle portion of the bubble shield.
The CPVC rod is part of the design and will be explained later as more progress ensues.