Linear actuator suggestion - fast , powerful and small
look into CO2 capsules, and the electric valves from softair-pistols (because they are geared towards the pressures encountered with those capsules, and they run on electrics with 9-14V) plus a small pneumatic cylinder (if you go with full pressure, those will act faster than you specced, but if you use the internals from a softair, the input is adjustable)