M40s are current issue and "in demand" as the old M17s aren't considered as adequate against NBC threats by survivalist types. You can usually find M17s pretty cheap now (actually looking at Knivezs' link, they have some M17 kits complete with the hood and filter and pouch, for $40).
They have some charcoal suits there, too. Be prepared to hate your life if you wear that in summer, it's like a non-breathable ski suit haha. And don't wear it around the house unless you like having charcoal dust everywhere.
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