I really don't see how this would hurt their business one bit. If anything, it would spread awareness of where the original design came from. The mold and the clones would not be for sale or trade. I originally said I would trade some "clones" in exchange for letting me borrow the original and I now realize this would be using the clones as a form of barter which would go against my ethics. Instead, I suggest paying straight cash to borrow it.
If I owned a clickclack myself, there would be no question about whether or not I would be ethically right to do whatever I want with it, so long as I did not profit off of it. So what if I owned one and I decided to make some resin casts to deck my keyboard out. Would you look at my keyboard and say I'm a thief?
These clones aren't even really clones, because that would imply they have the same material and construction. These clones would merely be plastic casts. Hobbyists do this all the time don't they? Is it unethical to make a cast of some R/C helicopter parts? I already have the original part and I want to make my own replacement part made out of urethane resin instead of abs plastic. By your logic, I should pay full price for the original product instead of putting in my own time and effort into "cloning" my own.
What if you saw a Van Gogh painting and you wanted to have a picture of it in your living room. Would it be unethical to take a picture of the Van Gogh (assuming people can take pictures of it) and then print it out to put up? It would obviously be unethical to sell the picture, but to keep the picture for yourself? Is there really an issue of ethics here?