Again, this is shamefully simple and awesome! Nice work!
This theoretically could be reproduced using acrylic instead of tubing (you'd need a dab of silicone to permanently seal it) if you have the right shape to heat-form it,.
I've seen people make bowls out of acrylic scraps by putting a ceramic bowl in the oven, with the acrylic sheet laying on top of it, and as the oven gently heats the acrylic, gravity causes it to droop and conform to the bowl. Removing it and letting it cool leaves you with something that's fairly smooth and nearly flawless in shape.
A metal funnel would probably work well for this but it would have to be a tiny one, and I don't know where you'd find such an animal.