Hey Sander,
Yes, there were many of clones. But I think it's fair to say that many of them just
copied the feature set of White Lightning and Fast Lightning which later became X-Copy.
The beast of the package was always Cyclone, which with the help of the hardware adapter
shifted the read line to the write line. The problem was the missing precomping and
refreshing of bit cells, but this was the best you could get back in the day.
http://www.youtube.com/watch?v=o2T9qpE6Jhw
The inventor of Cyclone, Rich Aplin, actually invented KryoFlux in 2008, about 20 years
after the original was made for the Amiga. :-)
http://www.youtube.com/watch?v=pOiWGj3A6Eg
Enjoy.