There is a modern batch of stones being mined, I believe in crete. They can be had in very large stones, and at one point, were about $55 with shipping in the US. They work just like my turkish stone (which I believe to be on the coarse side for turkish), but are a little bit more coarse yet.
Mine is a "white" type. The stones labeled black are apparently finer and may be a good finish stone, but the retailing of them is inconsistent and I haven't tried to get one. Shipping for a stone of any decent size from europe would be more than the price of the stone and you could get one with a giant inclusion front and center, so no go.
If that links works, that is one of the white ones. The shavers don't like them because they're not as fine as they want and they try to use them with water (I still have no idea why they try to use all of the oilstones with water)
Slowly getting to my point - you mentioned roubo talking about the decline in quality of the cretan/turkish stones. There may have been a mine area with excellent stone that's exhausted - or maybe it was a different area than the cretans now. I've seen around half a dozen of the stones like mine (but most are darker). with laminated steel, they shed particles and cut fast, reasonably finely and are easy to use (as is mine), but with softer tools, their aggression can be tricky.
Anyway, short on sleep and pondering around - since you read a lot more than I do, I was wondering if you knew anything further on the original turkish stones.