I'm not sure about the US, but I get mine from an Ebay seller here in the UK. They sell both the snap-on and pull-up variety, but unfortunately each colour only comes in a very limited range of sizes. I'd like to be able to get some that are large enough to go over doubled up nappies without being taut, as they are only noisy when they fit loosely with some space inside.
I got these two, and I love them. The material is quite thick and feels a bit like chlorinated latex - smooth but without the friction of untreated rubber, and it doesn't crease. They are very loud, but the sound is pitched lower than what I'd describe as a crinkle..Maybe more like a 'crunggle' sound. The closest analogy that I can think of would be a tarpaulin flapping in the wind.
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