The dosing pump is an enteral feeding pump originally used for tube feedings to patients that are unable to eat for themselves.  A semi permanent tube is usually passed through the abdominal wall directly into the stomach or intestines.  New they are rather expensive, however they can be found used in a variety of places.  I have bought several via online auction sites including Ebay.  I have paid anywhere from $20 each for a lot of 4 (great buy) to $75 each.  You can find them listed under both medical supplies, both human and veterinary, just search under enteral or feeding pump, or in aquarium supplies under dosing pump.  I have found better prices usually under the ones sold as used feeding pumps in medical supply listings.  I have several others in operation feeding newly hatched baby brine shrimp to juveniles throughout the day.