http://www.knowles.com &
http://www.sonion.com/
The truth is almost every universal and custom IEM is made with components from these two companies.
For dynamic drivers, they are often made by Foster, or sometimes developed by the company itself (JVC, Sony, Hifiman, Yuin)
Sony has broken the rule with the new Sony XBA-4 and that's why that UIEM is really interesting.
This is also why I was criticizing the AKG K3003, since if it's only a Knowles and a Foster inside then I don't think it's worth the price of a new motorbike.