If I recall correctly, the KiCost project learned a hard lesson about the ephemeral nature of things on distributors’ web sites. Links to manufacturers’ web sites seem to have a somewhat greater life expectancy but many of them won’t provide models or footprints until you create an account and present your pedigree.
Yeah, that may be the most practical approach. Something like:
The KiCAD standard libraries do not have footprints, or 3-D models, for this family of parts. There are too many subtle but significant variations among components produced by companies who manufacture this type of component. Please consult the manufacturers of the components specified in your design to obtain 3-D models and recommended footprints. KiCAD does not have any more information about these items. No footprints. No models. But have you noticed that people will read all the way to the end of this notice, even after they have been told that there is no reason to do so?