Executive Mentoring

Where to find individuals with as large as possible network of well established relationships with C board executives of public ( ! ) companies?

Hi, I'm looking for some suggestions please, where could I find people with as well as possible established business relationships (the network) with board members of public companies (publicly traded stock on stock exchanges)? Actually either executives (particularly CFOs) or non-executives. I tried contacting Executive Search firms but they declined me just because my inquiry has nothing to do with recruitment. Another idea I already got is using "business development" keyword phrase on LinkedIn and hope someone, within needed areas of expertise (corporate finance, capital markets, investment banking, etc.), will be stating on the profile that he or she has such network of known relationships with executives with whom he/she can get in touch directly at any time. No luck so far. What else could I do to find those people with said connections? Could anyone please help?