Tightly Stretched and Startched Nude Nylon Pantyhose Fabric
(The use of a Garter Belt would still be strongly advised.)
Actually, your description of what your hoping to find is nonsensical. Something that diffuses sound is not Acoustically transparent. Something "stiff" enough to stand or drape flat of it's own accord could not also be acoustically transparent.(...which again would also run contrary to being a "Diffuser".)
And visually transparent as well? To keep dust off a surface?
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