Unfortunately it is not that easy to get (a working) one.
And when you get one it could be defective like the latest I got that isn't "seen" by easynet/amitcp even if I checked before buying it that it was compatible (it should work with the cnet driver but I don't even get its mac address when I query the card within easynet).
As alexh said there are also many for sale without dongle so they are completely useless. I haven't understood yet if the dongles are all different or if it is possible to use a dongle with any (or at least more) cards but I guess that you have to use the specific dongle for each cards.
In a few words... good luck!
