I'm going to give you a personal experience.

I wanted some business experts to join a panel of judges and this was my "execution plan":

Research universities and non-profits where this executives or business people give their time.

Why? Most successful people that can teach (both are different skills) feel the need to "give back". So many of them volunteer their time and money on universities or organizations.

If you find those who have this characteristics you will be one feet closer to actually being able to reach them. This is because they are "minded" in helping.

To approach them I will recommend an exchange where they are not benefit of your conference but someone else is. If you tell a company owner that teaches "entrepreneurship" in a university that you want him to give. "Speech or class" and in exchange you will give 10 tickets for his students, he will be much more receptive of the idea.

The other strategy is the one you mentioned and it actually focus on two feelings: possible new clients (leads) form the conference or ego. I would definitely go for the second one, and instead of approaching saying "you will benefit from this" I would go for inflating his/her ego.

Hope this could give you some ideas.