This lens holder will help you use M12 (12mm) lens with Raspberry Pi camera board. It has the cut out for the camera ribbon.
For not threaded STL file, you will need M12x0.5mm tap to make the thread and 3 x No.2 x 6mm stainless steel screws.
If you printer is able to make small threads , you can try the threaded file.
Free to print for non commercial use.