Managers, talent agents, and agencies can serve a great role in your career if you choose the right one. While we will not supply a list of Elvis Impersonator agents here, the best advice we can give is to make very careful descisions, and to consult an attorney before signing anything. Yes, anything. 
Talent agents secure work for their performing clients. The standard agreement between an agent and Elvis Tribute Artist is by contract, stating that for a certain amount of time that the agent exclusively will handle all employment on behalf of the performer. That means every professional and paid booking would be contracted through that agent's office with a commission of the fee going to the agent or Elvis Tribute Artist agency. There is also "non-exclusive" representation, where an Elvis Impersonator will work with more than one agent or agency, with no exclusivity at either agency. In this case, it's the agent who books the date that gets the commission for that performance. The drawback is that this leaves much room for confusion, conflict, non-commitment and lack of loyalty.
A booking agent is also called a "buyer's agent". The buyers are typically live venue owners, special events planners, promoters/presenters, private or corporate event coordinators, brides/grooms and more. So those who work on behalf of the above to negotiate and broker talent would fall under the title "buyers agent" or "booking agent".
On this page we discuss Gig Salad, and a great benefit of their Premium membership level is the agent-friendly tools that are offered, allowing you to easily and quickly get your materials to your favorite booking agents. Check out Gig Salad here.