This is an attempt to provide a treatise on making 3D printable needle bearings with a twist.
This bearing has a "retaining rail" incorporating a V-groove in a standard needle bearing configuration. This removes the need for flanges or a specific thrust solution. The V-groove acts as a thrust element. You will find that in combination with the needle bearing, the thrust element removes stiction when a light thrust load is required with your bearings. Otherwise, it is simply a nice way to keep the needles in your races.
If you do the analysis, you will find another interesting feature about this method; the races are in compression when a thrust load is applied. The failure mode is intentionally the needles themselves. The narrow section of the needle is loaded in extension! This means that if you overdo the thrust load, the pins will fail rather than a hidden failure in the flange of the races.
Lastly, the provided information is really the gest of this submission. I will add additional models as they are requested, but for the most part, I am providing the information for anyone with a pencil or a full blown parametric CAD system can design the bearing they need. There really is no limit to how accurate or how sloppy you want to make these. I can see them in a very robust configuration for high load capabilities and in very sloppy ones for free-running applications.
Use your known wall thicknesses to optimize the bearing for your printer.
If you designed a bearing with minimal clearances, you will need to work with it to break each needle free. The more you work the bearing, the freer it will become.
I modeled this in PTC Creo 2.0. It is a parametric modeler where this file is easily configured for quick definition of many bearings using a common formula. For those who have a parametric CAD system available, you can enter the information as depicted in the provided diagrams. The pin-2-pin offset may require some explanation.