Tillers are really easy to make. Typcially they are glued up in mahagany and ashe. On a 28 footer you can make one out of solid mahogany. It is quite easy to rough one out with a jig saw or bandsaw and to shape it with a hand plane. The final trick is to use clamp the end of the tiller in a vice and do a final fairing and shaping by working a sandpaper belt aback and forth diagonally around the tiller. Put some varnish on and you are all done. The whole process takes maybe 16 hours spread out over a couple weeks.
Otherwise there are companies that make prefab tillers. I am drawing a blank on the name of the company that makes them but they are carried by both West Marine and BoatUS.