I got this paddle from Glasscraft marine in Adelaide for my young daughter. It cost $11 and she loves singing row row row your boat every time she grab's it
I'm sure they would be available at most boating shop's.
Great find Hilly. I just picked one up for my 5 year old daughter. Any ideas on what you are going to use as a T piece? Are you going to use an existing one or make something up?