Quote Originally Posted by Sirius Glass View Post
How about a bladder/bulb from a blood pressure machine?
How big are they ? I have the hand bulb part, as I use one with a Packard shutter and also pneumatic cable releases.

Quote Originally Posted by Greg_E View Post
How big does it need to be?

There are similar industrial devices, but I can't think what they are called.
Those look ideal, it's roughly 2cm diameter.