Jan, afaik slotting tools usually look a bit similar as parting off tools for a lathe, but with a strong shaft further up. As in shapers tools with inserts from square HSS work well, I don’t see why that should not work in your case. Bur the toolbit should protrude not more than necessary!
I made some small keyways in the lathe with such tooling (reciprocating the screw-less topslide with a lever, as described in umpteen classical ME books.
Greetings, Hansrudolf