I can tell you from experience that the handlebars on my 400SC sucked.... They're on the parts shelf gathering dust.
The replacements are Renthal bars listed for a TRX300 and TRX250R and the medium ATV diamond grips.
My wrists hurt after about an hour of riding with the stockers. I spent about 90 minutes riding a lot harder than before with the Renthals and haleluah!! No arm pain!!!!!
P.S. If you have an air compressor, blowing some air between the grip and the bar will allow you to slip the grip on. Be careful if the grips don't have a hole in the end or you can launch the across the shop like a champagne cork. ( The voice of experience ).

 

Another helpful tip on grips. If you have large hands, or if the grips seem like you're grabbing a pole, try some prodesign grips that are tapered. They are soft and larger in diameter in the center. They seem to last a very long time also.