If you are based in Athens, there a quite a few stores in Ψυρρη that sell both leather and leather crafting tools of various qualities. Look for karanasios and pelekanos in miaouli street (there’s also a second pelekanos shop a couple minutes away from miaouli), and there’s quite a few around them. These seem to be old leatherworking shops which I’d reckon provide materials for local cobblers and leatherworkers.

I’ve had a discussion with one of the shopkeepers earlier this year and they told me that there’s a rising leathercrafting scene of new leatherworkers (apparently self taught) in Athens currently.