Military surplus gas masks IN GOOD CONDITION (no dry rot of the rubber, may or may not come with hood), with SEALED (in pop-top can) filters should be fine. As an aside, you WILL pay for the privilege...expect $80+ US. Anything less probably means you'll be inhaling something you didn't expect....
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Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, a critter that can be killed but can't be tamed. --Robert A. Heinlein