Where can I find a Sigma 50-500mm f/4-6.3 EX DG HSM AF Lens for Nikon SLR Camera?

I'm looking for a store that has this lens still available. I know they were discontinued by Sigma earlier but I was wondering if anyone had some left over.

Example of such lens can be found here:
http://www.bhphotovideo.com/...EX_DG.html

I would consider Sigma 50-500mm f/4.5-6.3 APO DG OS HSM SLD Ultra Telephoto Zoom Lens for Nikon Digital DSLR Camera
Designed for use with full frame digital SLR cameras.
10x high zoom ration ultra telephoto zoom lens
Offers Sigma's OS System allowing handheld photography even in low-light situation
HSM ensures a quiet & high-speed auto focus

http://www.amazon.com/...003A6H2Y8/

http://rover.ebay.com/...m270.l1313

KEH Photo has three of them used on page 5 of the link below

http://www.keh.com/Camera/format-35mm/system-Nikon-Autofocus/category-Non-Mfg-Zoom-Lenses?s=1&bcode=NA&ccode=9&cc=55956&r=WG&f