Yeah ... I'd suggest just making his own faceplate for something like that .... and make it from wood.
Make the center hole just a tiny bit undersized to fit on the spindle and screw it right on .... Then take some CA on an applicator pad of some sort and wipe it all round the threads inside. Once it's cured, screw it back onto the spindle to make sure it'll work. At that point, he can turn the faceplate true to the spindle and face off the front .... ready to use!
However, 99% of lathes I am familiar with should have a right-hand threaded spindle. It's relatively easy to get 3/4" x 16 nuts in the right hand thread and use those as the mounting point ... just drill a hole in the faceplate board for the nut, cut out some corners with a chisel and epoxy it in as flush to the face as possible. Mount and turn it true just as you normally would, facing off the front as well.
In either case, you want your faceplate to sit flush against the spindle shoulder. The threads merely lock it in place, tight against that shoulder. The shoulder is what holds it in proper alignment with the spindle.
(just thought about it a minute....)
Is this for outboard turning? Mounting something on that reverse side of the spindle? He may want to use the method with the metal nut for his faceplate, but rather than around a dollar a nut those things will be upwards of 5 dollars apiece, plus shipping ... he most likely will not find them locally.