Not exactly sure what type of end prep you are talking about. But you can by dowel pins the size you are talking about at any industrial supply store. Dowels are hardened and ground solid pins similar to needle and roller bearings. (The difference between needle and roller bearings is the ratio between the length and diameter.) Not to be confused with roll pins, some times called split spring pins. Those are hollow pins with a slit down one side that extends from the outer edge to the center.

Hope this helps. If you can give a better detail of what you are looking for I will try to help further if needed.