If that doesn't work, you may want to look at
hobby-shop thinwall
brass tubing to fabricate your own tool. It's quite inexpensive and
the brass is easy to work. The operative magic incantation is "K&S
tubing".
Most good model shops over here have the rack of K&S metal rods, tubes,
strips, etc. Very useful...
_BUT_ I don't know what alloy the brass is, but it doesn't machine as
well as the 'CZ121' brass. Not a problem unless you intend to stick it on
the lathe.
-tony