They look a bit rough around the edges
It is exactly the same quality like the five basic color ones (sorry for the reflections of my scanner - I don't have a digital camera).
Do you recall where you got them?
Unfortunately I don't remember who was the seller (the only thing I know: it was a German seller). The auction took place shortly after the Celebration expansion were released. So I assumed, additional colors will be available in short time. I remember I have looked on ebay for several weeks in the hope to get some more colors, but there were no auctions anymore. Additionally I searched in the web the shops of all known dealers of board game accessories. With no result. I fear, I cannot help.
Did they use Carcassonne in the description?
No, definitely not. If you search German ebay, use the string "Spielstein*".
By the way, are you ready to sell yours?
No, of course not.