On my Catalina 22 I have a tiller tender which has served me well for many years — and it didn’t cost a cent.
On top of the tiller are two pieces of 3/8″ x 3/4″ hardwood about 5″ long. The two pieces are drilled horizontally, at the joint line, about 2″ from the end to accommodate a 3″ length of split neoprene which has an inside diameter slightly less than the diameter of the braided line which runs to the coamings. Two holes drilled vertically near the ends are used to fasten the device to the tiller.
The clamp is a short non-ferrous machine bolt and nut from salvage. The nut is epoxied into the bottom face of the lower piece so that it is flush with the bottom. A knurled knob is epoxied onto the bolt head. Some experimenting needs to be done to get the right length on the bolt. When tightened down there should be a small gap between the two pieces. This bolt assembly is about 3/4″ from the forward end.
Many times I have sailed with this tiller tender for twenty or thirty minutes without touching the tiller.