Find them on eBay. One with all the cutters will set you back nearly a grand, I reckon.
As for the size, the cutters are adjustable. You can go about a 64th up or down, but because it’s cutting around the dowel, you can get some tear out if you’re not careful. As with cutting threads on wood, some woods benefit greatly from a soak in linseed oil before cutting. But once you dial in a cutter, you only have to readjust it when you sharpen it.
I have mine all set to about 1/128” fat, so I can run a piece of 60 grit down the length to take off any small splinters and be pretty much right on the money. Walnut, birch and beech all go dry. Oak and ash get soaked first. Poplar is also pretty well behaved. Pine is a pain in the ass pretty much no matter what.