There are some white aluminium oxide slip stones about that will do it. Some are sold for dressing diamond wheels.
You will find what is needed by googling slip stones. The one I use is dark brown/orange, 3/8" square and about 4" long and rather fine. The white aluminium oxide ones are generally coarser. The best type is often called india stone.
The diamond hones are fine but at their best used with honing oil. The slip stone clog up with hss over time as they are usually used dry. The diamond hones can be used to clean them up.
The one I use is probably natural India stone. It knocked a big hole in my tool bonus when I was an apprentice. Various grades of aluminium oxide should be as good. The modern version can be bought here
**LINK**
John
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