Do they make such a thing? Im looking for something similar to the DX lens for the Nikons, and I am not having any luck.
I don't know if this is any good, but I've heard good things about it... http://www.tokinalens.com/products/tokina/atx107afdx-a.html
I'm not sure what the OP is looking for. FF usually refers to cameras...or lenses that can cover those cameras. Practically every SLR lens for this format is full frame on the 40D because it's a crop body.
It was my understanding that a full-frame fisheye differs from a circular fisheye in the appearance of the image. http://www.vrphotography.com/data/pages/askexperts/basics/fffeye.html