OK not sure why but I feel like I sort of sent you down a rabbit hole. I asked on the z650 proboards site about the grip for the F model bikes as was told they are like hens teeth, you will not find one.
You did ask if there were other grips from other bikes that might be made to work. I do not know off the top of my head if any other units would work on a 650. I think the issue would be the length/distance between the connections points.
Kawasaki did make another like grip for the 650 H models (these were sold in the US unlike the F2 F3 F4) The part# is 32109-1016. It is my understanding, not saying my understanding is correct, that the connection points are not the same on the B, C and F and is not a direct bolt on. It is also my understanding the the above part will work a 750 twins.
Others here may be able to measure the connection points on the different models to see if any will fit.
Sorry for sending you down the rabbit hole!!!!!
