Try using a rocker switch
Y'know, if I were constructing one of these masks-with-a-fan, I'd use a rocker switch like this one:
There's a lot of different models, but I suspect they all would work. Here's a link.
Shane Allen, aka T2
"You've got to ask yourself one question. 'Do I feel lucky?'... Well do ya, punk?!?" - Clint "Dirty Harry" Eastwood