These are nice: http://www.ergon-bike.com/en/grips/index.html

I have the GC2 model. Some bike shops have them, or you can order them online if they interest you.

They don't extend as far as traditional bar ends, but they are adequate for standing and give you another hand position. The primary benefit is the ergonomic shape helps prevent hand numbness. I think they help dampen vibration a bit also.