I'm a relatively recent convert to bar ends and wish I'd bought some years ago. They have made a a big difference for me, not just with climbing but on those fast flat sections where you can stretch out a bit, similar to riding on the hoods of a racing bike.
If I was to replace my current ones I think
these are the ones I'd get.
Assuming that you have standard size bars, they will just clamp on. Depending on what grips you currently have, it might be necessary to cut the ends off to allow the bar ends to fit (or change to grips designed for bar ends -
example) and you might have to adjust the position of the brake levers/gear shifters inboard slightly.