That was a good Google Rutty. I was looking for something similar a while back and ended up getting something poor from a far away foreign land.
Of course they are Metric and Tuckers (If thats what it is) are Imperial. so a measurement would need to be taken of the thread on the rod and identify the thread, then get a knob that could be drilled out and the same thread as the rod put into it. Unless one would be luck enough to get the Metric thread to go onto the threaded rod and glue it in position. Not ideal, but a result of sorts.
Jonty