I'm looking for something like this air valve:
(as discussed in https://engineering.stackexchange.com/a/12404/12007)
But I need to tube to be wider (3/4 in), the tube to be shorter (the shorter the better), and I would like it if the mechanism for opening and closing the valve wasn't so bulky. This is a picture of an air valve at a much larger scale:
I'm hoping to find something like that at a 3/4 in scale, where the mechanism is proportionally smaller also.
I only need the valve to be able to withstand the pressure of a person exhaling, which I think is like 3 psi max. So I'm hoping something less bulky than the solenoid in the first link could be used.