MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
This one I made for igus bushings. The OD of those is 12mm. Should work for you. https://www.thingiverse.com/thing:2538263
The hole is modeled at 12.3, and on my printer fits the 12mm OD igus very well.