There are no "voice acting agents". Agents represent actors of all kinds. Voice actors are simply actors who landed a voice acting job, among other acting jobs. Agents make money when their client books a job, and the simple fact is there are not enough voice acting jobs for agents to make a living off. So it wouldn't even make sense for them to be "voice acting agents". If you find one who says that that's all they are, they're not legit. Also, you don't "find an agent". They find you. The chances that you cold contact agents and one will sign you are close to 0. That's not how it usually works.
I suggest that you take the first step of going to a good acting school and getting regular acting experience (theater, indies, student films, etc.). You're not gonna get any voice acting work if you don't become a regular actor. And you can't become a regular actor without the above. No agent will take you on. Instead of worrying about things you're not gonna have to worry about for at least another decade, worry about getting the training and the skills. You'll learn it all in a good acting school anyway. There's so much more to it than you think.