Have you used one? If not, I fear you might be disappointed, so suggest you try it to make sure it will do what you need prior to investing a lot of time/effort/money. Two primary issues, 1) you're scraping a spindle turning, which yields a terrible surface, so you can't get to actual final dimension because you need to leave a significant amount of material to allow you to sand or finish cut to a smooth surface and 2) it won't replicate fine detail, being limited by the shape of the cutter and, again, the need to leave enough excess material to sand or cut to a final surface.
I've found it worked better to set up a marking template to get elements at the right places along the length of a turning and then as many go/no go gauges as required to set key diameters. It's pretty easy then to fill in between your marks by eye. Just as in fitting a box lid it's possible to size components to a few thousandths of an inch by hand with gouges and skews; I was never able to accomplish anything like that with a duplicator due to the tearout.
Probably not so important for your use, but doing it by hand is also a lot faster, for example if you're doing lots of balusters. A gouge or skew moves a lot more wood quickly than one of those scraper points.