Congratulations on creating a 50's club. That sounds like a great idea and a fun club. If you are seeking entertainers, I would try first by contacting gambling casinos that hire famous entertainers. For instance, in Las Vegas as well as Reno and Lake Tahoe, Nevada, many casinos promote and hire entertainers. The marketing department or promotions department I feel would be a good resource for contacting the entertainer. Many singers have agents, so the casinos may be willing to give you the name of the entertainers agent who then could give you an idea of how much the entertainer charges per engagement. Good luck and I hope this off beat idea helps.