Do not know if this particular solution to a seemingly similar problem....here goes, WW2, (I'm old), training using gas masks. If you wore glasses and put the gas mask on extreme fog and mist on glasses. We were issued a product, exact name escapes me, either 'anti-fog' or 'anti-dim'. Stick form, similar to solid state deodorant. Round about 3/4 inch dia. It really did the job.
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