I was just thinking about bone today and found this topic. What about using bone as a spacer between the handle and shank. It seems to me you could use the long bones of a deer (people who don't hunt here are the exceptions). Select a length that is the appropriate diameter, say between 1 1/2" - 1 1/4. Then either pre-slice them to the desired height and fill with epoxy or leave the whole length for slicing later, then fill with epoxy and slice it once the epoxy's cured. Once you have the slices, drill a hole for you screw down the middle, attach it between the shank and handle then sand it to fit just like any other wood spacer. I've never tried it but it may work.