Best fisheye converter lens for Nikon?

I don't have the cash for a real fisheye so i just want to buy a converter to put on my lens, but i don't want to see the edge of the fisheye when its on, and i want to know what would be the best one to get.

I'm not sure if you can get one, but if you can it won't give quality results.
I've got a 10.5mm fisheye and its really great, capable of some wacky shots.

You can use certain software to create a 'fisheye' look to your pictures.

Just cr*p on the lens.It'll do the same job and cost less.