Does anyone know where I can find the other 3 intertainers? I have the one from novac.

Human Male located to your right just after you enter the Strip for the first time. You can't miss him, he's the guy telling jokes.
Ghoul Male located near or on the stage over at the Wrangler Bar/Casino

I'm still looking for last one.

FYI, the word is "Entertainers"

It shows them on the map/composs with a quest marker. one to the right of yo when you enter the Tops section of the strip while coming from the Gommorah area. An other is a ghoul in the Atomic Wrangler. Last is a cowboy near the Sunset Sasparilla bilboard that is close to the El Dorado Gas place.