Any motor parts stockist should sell them - its just a
two-pack of filler and a piece of light guage steel which, with the help of a hose clip (or two) bandages the hole.
Remember to clean the area first with sandpaper so the filler putty takes hold properly.
http://www.caswellplating.com/permatex/images/perm80334.jpg
http://www.pond-equipment.creativefountains.com.au/Pumps/Plumbing/ss%20hose%20clip.jpg
Mike.