Curious what your project is???

How long do you need them to be and how many?

I've always just made such things as needed. You can plane bone with a hand plane; the best I've found for the purpose is a low-end Stanley low angle block plane sharpened to a very short (high angle) bevel. Harder irons tend to chip on the bone, and actually get dull quicker, in my experience.

To make a rod you start with a piece with a square cross section and remove the corners. A block of wood with a 90 degree grove in it, and a stop block at one end, holds the square bone at the right angle to plane off the corner. You start my main it octagonal, and keep removing corners until you run out.

A scratch beader can be used to refine the rounding over. File a semicircular bite with the right radius out of the edge of a scraper. The burr from filing acts as a cutting edge.

If you need it to be really round you can chuck the rod in a drill, and use sandpaper to remove material while it's spinning.

I make small bone rods this way all the time to use for fret marker dots.

I would think a high-quality plug cutter (Veritas or similar) would give you what you want. The plugs are tapered at one end but I wouldn’t think that would be a problem.


Steve

For these projects, I use a Taig hobby lathe.
Banjo pips are normally around 1/8" and IMHO are too small for guitar post saddles.

I would do the same John as I have a Taig as well. I've used the metal working accessories for making bone bridge pins. Bone dowels would be pretty easy using the cross slide I would think.