George,
Your best bet would be to buy a set of naturals (caps) from an organ supply company or builder, such as Armdt. The caps are normally glued or screwed to the top of another piece of wood which contains the spring and notch (keystick per se).
If you have the tools, you could also make the tops fairly easily from solid maple, then use a router to create the bullnose profile and roundovers. The naturals are normally coated in a hard laquer or epoxy to help prevent wear.