I read a piece on another forum about a guy who was building a DIY peristaltic pump from some silicon tubeing, a couple of skateboard wheels and an axle/motor thing. basically, if I remember correctly, the skateboard wheel pressed the tube between itself and the inner wall of a cylinder so when the axle rotated it would continuously squeeze the tube as it goes around. a couple of wheels keeps the action going constantly.
well that's about as clear as mud, but perhaps some of you engineer types can make something of it.