http://www.ifebp.org/cebs/usprogram.asp
They do not have an online membership directory, but you can contact them from the above website.
As Stephen says, there is a printed copy of the membership directory that all members of ISCEBS receives. (ISCEBS is the International Society of CEBS. If they received the CEBS designation, but does not keep up their membership, I assume they would not be listed in the membership directory. Therefore, someone may have passed all of the exams, but is not a current "CEBS."