Hi Ian,
I've just been using a white sheet of paper (or anything white - son's T shirt etc etc) in the ambient light I'm going to be shooting in. It's really rough but seems to work for the happy snaps.
You could fork out $20+ or so for a sheet of 18% Grey card which is the CWB standard method.
http://www.digitalcamerawarehouse.com.au/prod2937.htm
I may try out the lens hood you linked too - at $9 it's worth a go...less cumbersome than a sheet of grey card in the field!!
Thanks for the link.
Doug