Originally posted by paulh If you don't mind the looks of a rubber hood, they can be had very cheaply. The 3-position collapsible ones work well - they screw onto your lens' filter ring.
I believe these are the best replacement if you can't find an OEM. The problem with super-zoom hoods is they have to be wide and short enough to not vignette at the short end, which means they don't do much at the tele end. With the rubber ones, you can just collapse them back for wide-angle shots and pop them back to full-length for everything else.
FWIW, Sigma has a great hood design on some of their zooms, the hood attaches to the outer lens barrel, (not the part that moves during zoom) so when you zoom to wide angle, the hood effectively becomes shorter, and vice versa.
Ron