The need for this design became obvious just a few days ago, so the design is still in process. So far, I've chosen 1" PVC for the syringe body and 1/4" plastic tubing for the delivery tube. I've started designing the parts in FreeCAD. The plunger will be driven by an 8mm threaded rod turned by the NEMA 17 motor. I need two smooth guide rods to mount along the sides of the body to guide the motor. I also need two threaded rods to hold the discharge and the drive nut holder in place at the ends of the body. A good sketch will make all this clearer and a trip to the hardware store should provide the precise parts so I can finalize the design and start printing the first version.

Here's the motor mount. Still pretty rough, no guide holes since I don't have the rails yet.