Fabricated a new tillerhead out of two pieces of C360 12" x 1" x 1/4" brass bar stock.
The tillerhead that was mounted at the time of purchase broke on the first day of the 2019 Annapolis NOOD as detailed on 2019-05-03. All attempts at finding a suitable replacement have failed to provide a fully satisfactory result. Decided to abandon the effort to find a commercial solution and create a "custom tillerhead" from brass bar stock.
Used the existing tillerhead and tiller to determine the location, spacing, and size of the bolts. The rudderhead is ~3/32" wider (athwartships) than the tiller. Crafted a shim to sit between on of the two pieces of brass bar stock and the tiller to make up the differnce. Lacking a planer, I sanded down a piece of 1/4" wood using a quarter-sheet sander till the required thickness was left. Epoxy coated the shim to protect it from the weather.
While the effort took much longer than expected, the result appears to be quite serviceable...better than any commercial solution to date.