Just curious as to why you need what you need?
Is it because you'll be shooting something that is moving fast in low light?
If you can get by with 18mm on an APS sensor, the Sigma 18-50/2.8 EX DG Macro is very sharp wide open and extremely sharp a few stops down. This is a crop-factor (reduced image circle) lens, though, so it won't work on a FF camera.
If you're using an APS sensor-equipped dSLR, you can use the Zenitar 16/2.8 fisheye, and because of the crop factor you won't get the extreme fisheye distortion (you will get some barrel distortion). I don't know if this is or isn't acceptable, but at $150 to $250 depending on the eBay option this may be a good alternative.