Use this simple pump to move fluid around in small quantities. It may require more torque than you expect.

Assemble in three layers from 6mm plywood. All holes are sized for the metric hardware I had on hand. Use 608 skate bearings for the pressure rollers; they go in the locations indicated by the green circles in the plans. I added washers between the layers for spacing. This was necessary to get rid of unnecessary friction on the bearings because they're a bit more than 6mm thick.

Run the tubing in and out the notch in the bottom, going around the inside of the raceway. The bearings should smash it completely flat and make a watertight seal inside the tube.

You may have to move the holes on the rotor arms in or out depending on the size of your tubing and bearings.