The tool of choice to get to the D/R Marine home page is google.
Not everybody likes to do their own woodworking - no matter how easy.
(Although I'd personally go that route every time).
I like the PhD handle suggestion. Just want to observe that the forces that act on the "fork" side of the tiller are substantial.
Through-bolting the two "tines" where they meet the stem helps, and even on my tiller which is made from a single piece, there's a boat nail fitted from side to side that's supposed to prevent the wood from splitting. Even if the wood cracks, the tiller can't pull apart readily.
However, there are two other places where it may be worth guarding against splitting, and that is where the bolt goes through the two tines and the rudder head. Each of the "tines" should be supported against splitting horizontally, for example by drilling a small hole top to bottom near the end and placing a #6 bolt with nut.
Even if the wood should crack, these bolts would prevent the hinge bolt from pulling out of the end of the tiller.