Look for something that has a 3.6mm or 2.8mm lens option (I use a 2.8mm IPC-HDBW4231F-AS [an older model] and I don't find it to be distorted, certainly not fisheye, but try an EYEBALL instead of a dome camera). You could also look at something with a manual varifocal lense so you could dial in your area of interest and not be locked into a specific lens angle.
Just realize that a wide angle camera like that is only good for overview, you can't actually ID someone unless they are almost on top of the camera. I know you mentioned you weren't interested in multiple sensors, but after using my wide angle 2MP starlight camera for a couple years I want to swap it out for a: IPC-PFW8802-A180 multi sensor with 180 degree field of view because crap always seems to happen "off camera"! So just recognize it's probably an eventuality you are going to want a lot more than just an overview camera.
It seems that about 110 degrees horizontal is about the widest Field of View on the camera market, for single sensor, non-fisheye/panoramic/360 cameras. To get more horizontal FoV you have to use multiple cameras or one of the types I mentioned.
