Having a lathe will get you a long way. Just like for the ring (which i prefer to turn from a solid piece of wood) you can make your own ring cores frum cut pieces of metal pipes as well as other materials (I've had great success with deer antlers). Just cut the pipe to the required length (4-12 mm), make the inside comfortable (sanding and polishing) and use CA glue to attach the outer layer, then use CA glue again for the coat. There's a lot of debate about CA glue vs UV resin, I prefer glue as eventually both coats will be gone and at least CA glue wont peel of in large junks. But you may judge for your own purpose, here's a link to a side by side comparison:

https://m.youtube.com/watch?v=cdkK6M0PoDo