I very much doubt that those bowls were "3D Printed". Not that I doubt John Olive's honesty, I most certainly do not, but the only way that degree of precision and clarity can be achieved is that the "printing" is done by lasers directed into a bath of the appropriate melted plastic, the laser "hardens the plastic at the point of focus.
The Dollar value of the machine that can do that has lots of zeros on the end of it.
Those bowls were cast, and as I know from my abortive attempt to make instrument pods, the process of making the moulds is non-trivial.
All that said, I doubt that the plastic bowls would have the kind of impact resistance I want, and will cost a lot more than a piece of tube "sight gauge" - particularly when in all seriousness you need to reset the float level about every second blue moon.
