Thanks for the thoughts. This might also provide an explanation why Fairphone is not offering individual earbuds (not that it is a solace … 
).
@carl1 I think it would be good if you kept this search topic nevertheless. In case there might be an earbud match, it would still help to find out if uppercase’s reasoning can be verified or falsified. In the worst case, you might still be able to help out someone else with a simpler request.