I have a long history of oil stones as well as ceramic and diamond.
Real stones are still available but either old ones at flea markets / yard sales/ car boot.
Or, search on line for Washita stone nearly mined out but still producing in usa though word is much lower grade than they were.
There are others available, some from belgium and I forget where else.
These days I use diamond plates, convenient, quick and cheap to get my edge then strop to a finish.
Recently the wife bought a set of red corundum rods. They are about 4 inches long and go from 1/16 up to a 1/4 inch.
Took a while to get used to but so easy.
Good luck.