https://www.3riversarchery.com/pdf/BarrelTaperSanders.pdf Tim's Taper Tool works off a combination disk and belt sander and not only tapers the nock and point but will also taper the shaft itself. I have used one of these for years, and it works as intended, although is a little finicky to get set up, and I generally burn through a fair number of practice shafts before I manage to get it adjusted the way I want.
The part that Tim makes is high quality woodworking, held together with brass thumb screws, tension springs, etc. It works with a number of commercially available combination disk and belt sanders. Mine is a Ryobi. I probably wouldn't have bought the sander other than to use with this taper tool, but it has come in handy for a number of different projects unrelated to archery since I bought it.
I don't see this currently listed on the 3 Rivers website, but the .pdf came from there, so maybe it's still available for special order. It looks to me like it required a lot of work to make for the amount it was sold for, so it was probably a “labor of love.” That kind of thing tends to get old after a while if you're not making much money from it.