West Marine and Defender and similar sites sell laminated replacement tillers.
You can also laminate your own, if interested, with simple tools. For a 25-footer I once just sawed one out of a plank of oak using the original as the profile. Unlike the original, it did not break in half whenever I, uh, accidentally sat on it.
I have my original delaminated tiller but I came to the conclusion that it just wasn’t worth the time to fix it , so I bought one from west marine that looks like gargrags. it’s very well made. I had to epoxy some hardwood to its base in order to make it wide enough to fit snugly.