You could try calling AFTRA in Los Angeles... it's the union for television and radio personalities... they could provide some guidance and contact info for representation. They probably won't be able to offer a lot of rate info. More than likely, that will need to be acquired from agents... if they have them. Years ago when I had my advertising agency, I hired William Shatner to make a personal appearance. He was in between agents and I worked out a deal directly with him. This was, of course, after Star Trek, but before the show found cult status and long before any movies were made.
Point is... these people struggle sometimes just like everybody else. You never know what's possible until you try. The people at AFTRA are likely to know who's hungry for work.
