I don't know what it would cost, but you could try this: Bend a piece of stainless steel sheet into a trough, then weld plates on the end and Voila, a long tank.
I know that labratory supply stores would have the black stoppers for sure. I can't see it hurting to test the yellow earplugs. A good test would be to slip a piece of paper down a steel tube, stuff the ear plugs in the end and then put it in the bathtub for a bit, if the piece of paper is wet, they don't work, if it's dry............
I think if you took the sheet metal to a welding shop, they wouldn't charge you too much to weld on the end plates.
I've never heard of it......which isn't to say it's not possible....
Maybe if you used red iron oxide instead of zinc oxide? ?? But I think it would come out more of a rust colour than red....if it worked at all.
Short answer is no, lol.