IGNORE WHAT I SAID BELOW. I GOT IT WRONG. SORRY FOR ANY INCONVENIENCE.
I was having a tidy up in the garage and came across some Pazzo levers for a 2006 Suzuki GSX-R1000 K5/K6 (my old race bike) and out of curiosity I wondered in the clutch lever would fit a BoxEye FZS600.
It did!
I have the bike in pieces so I can't road test, but I am fairly confident this will work no bother. Mention it in case anyone needs to replace a clutch lever, you now have a bigger choice.