I ordered a couple from an Amazon vendor, but they never came.
I ended up making my own tools. For one, I sawed off the handle of an
adjustable sink trap wrench and welded an old 3/8" socket onto the
handle stub at right angles. This allowed me to put an extension
and a ratchet on it and get enough force to lock the locking nut.
The other tool was one of those flat stamped sink trap wrenches.
I heated it in the middle with the torch, and bent it at 90 degrees.
This provided a way to hold the packing nut while tightening the
locking nut.