I have a feeling that it will always be difficult to discern idioms in one's own language . This is probably the cause of the meagre results of your search. Idioms, as I understand the term, comprise those parts of a living language that cannot be deduced from rules. To a native speaker, rules are secondary phenomena of rather variable importance. Idioms cannot be identified because they form a continuum. Only from an outside perspective, based on language learned from rules, you perceive idioms by stumbling over them. So as a practical hint, you might start your search in foreign english-teaching literature.