I once used (in my college student days!) a curtain rail as a tiller extention. I have also used the tube from an extending boat hook as a tiller on one boat. At the end of the day an aluminium tube is an aluminium tube. My advice is to think outside the box, and pester your local chandler for an old something or other to do the job (returned sales hanging about that they wish to get rid of is a favorite!)! How about an old mop handle from those aluminium mops with the screw on mop head? Cost effective it is - not to mention recycling is good for the environment!