You're going to be able to find just about anything camera related on B&H if you search around a bit.
That lens is not a fisheye, it's a wide angle. Kenkos are ok, but if you want a fisheye, get this one:
http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=124579&is=REG&addedTroughType=search
It's basically a step below the $300 Century Baby Death lens. Take out the Macro when you get it if you want to significantly increase the width of the lens. I would personally save up and get the Baby Death, since the difference between the Kenko and that one are like night and day. But it's your choice, if you're looking for a fisheye and you need one right now, this would be your best choice.