"macmetex" on Ebay had the Futura II ethernet daughter cards. I don't know if he still has any. I think I got the last of the 10bt ones he had, but he still had some thinnet (coax) cards when I last checked. He also had some Futura II SX cards in the box, but I already had one of those.

My experience with the Futura II card and the ethernet daughter card is that the machine will lock up when Open Transport extensions load. If you use Classic Networking, it works great, but with Open Transport it locks up the machine.