How about a foot pedal operating a solenoid?
Looking into this at the moment, where could I get a suitable 12v solenoid, the only ones I have or can see in catalogues are just for switching?
Or even easier, a foot pedal pneumatically operating a "finger".
The latter would be safer as the amount of force and the distance of travel would be more easily "modulated" by your foot action. (and it may be quieter too)
Pneumatics! Nah, dont think so, this would require some sort of air pressure supply wouldn't it?