If you have a metal working lathe, why not make one? An
appropriate block of aluminum, brass, bronze, or steel would be
adequate. Cut the taper you need, but small enough to install a
slot for a single edge cutter. It can be as simple as a piece of
file, saw blade, old plane iron, whatever. Set it deep enough to
have a set screw to hold the blade. You don't need much of it
other than the bevel out to cut, a bit like a plane iron. It will
require cutting a straight sided lead hole to start in.
You never said what kind of taper you're looking for. Ridgid
makes a pipe reamer that would cut wood and give you a taper,
though it might be more than you want
Keep the whole world singing . . . .
Click to see the full signature.