As long as you haven’t signed an exclusive agreement with any one agent, you can have as many agents as you want. My advice though would be to be honest with your agents, especially with the ones that get you most of the work. It could happen as happened to me a couple of years ago, that I got called in for the same audition by two different agents within 15 minutes. I accepted to go to the audition from the first agent. When the second agent called, I told him that I had already accepted to go to that audition. In that moment, I was so glad that I had told the second agent the truth, which was that I had another agent as well. Even though I wasn’t obligated to tell him, I was thinking it might be better to be honest, which would help maintain a good, open relationship.
I just think it’s always good to be clear up front. Takes the stress out of life. There’s enough of that already.
Hope that answers your question.
Here is some information about how to actually go about getting a talent agent.