I previously had printed a GoPro tripod adapter that utilized the GoPro quick release clip. However, I have a small tripod with its own quick release and just wanted to adapt the ¼" tripod thread directly to the GoPro, so I drew this up in SolidWorks. The threads are modeled directly into the print; I used 0.2mm layer height and they came out perfect. 

You will still need and M5 nut and GoPro thumbscrew. If you would like a version with the M5 threads printed in as well let me know and I can make a quick modification.