I picked up a Precision 3660 over the holidays.  While outfitting it I came across the hot swap bays Dell makes.  I was able to easily locate a drive caddy for 3.5in.  But I am having a heck of a time finding the actual flexbay to mount to the chassis.

the image is from the 5860 build page.

from the build sheet;

But I have thus far not been able to locate this item either by Flexbay or any combo of the part numbers above.  Anyone have any ideas?