@Gerhold-Ten-Voorde , our lens holders are custom and we do not have any information we could share about those, but you may be able to find similar lens holders from other sources.
IMX412 : https://www.m12lenses.com/M12-Lens-Holders-s/61.htm
For IMX664, you may want to check Runcam fpv cameras, which appear to have similar lens holder / housing, however i don't know if those would have extra threads you need.
Also, please note that if you are going to try the spacer approach, make sure that there is absolutely no gap between the spacer, lens holder, otherwise light can enter the camera from the side and affect the image quality. Also make sure that even when using the default lens holder with IMX664, the mounting holes in the aluminum housing are covered, so that light cannot get inside.
Alex
