I stand to be corrected here, but I think just about ALL bar ends fit over the last 2 or 3 cms of the handlebar, so you have to move the gear shifters and brake levers and the handlebar grips towards the centre of the bars. It's a bit of a chore to do, but it's not actually that difficult.
I sort of can't believe that no-one makes bar ends that mount INSIDE the handlebars, so you can still use the whole width of the existing bars. But it looks as though no-one does make such a thing.
Unless any forum members know differently.......