"Walt Cheever" wrote: (clip) Having a machinist make them might cost more
than the lathe.
^^^^^^^^^^^^^^^^^
That is certainly true. However, the problem will be finding ferrules that
fit tightly on the existing handles.

Ferrules are there to keep the wood from splitting, and to snazz up the
appearance. You could possibly wrap the handle with closely spaced wire
winding, and then solder or tie the wire--if you don't care about looks.
You might be able to shave off a little wood to make the available ferrules
fit. Or, since you this newly acquired wood lathe, you could use it to
make some wooden sleeves to "fatten" the handles to a size that fits an
available ferrule.