I doubt that a reliable function of this sort could exist.
LowerCase("fontname") does not point to a single unambiguous entity, even sometimes on a single OS, never mind across the plethora of possible systems.
This is one reason many word processing file formats provide for embedding of specific fonts, to prevent the "wrong" font of the same name being used accidentally.
Also font foundries extend their fonts from time to time, and continually introduce new ones such a function would not know about.
I suspect you will have to trawl through the font data for the fonts you have available and discover this information, as it currently exists for the fonts you have access to, for yourself.