Hi, John,
My tiller is made of ash, which I think is generally the wood of choice for tillers.
My suggestion for sourcing it would be to look up a local joinery shop in the Yellow Pages and see if they have an off cut of a suitable size they could sell you. They should also be able to cut out a blank for you on the bandsaw for a fee, if your DIY skills don’t extend that far.
Charles
W2