I can't help you with replacing the whole grip, but I've got the Grip Puppies ($8) and they help with comfort a lot. I agree that std BMW grips stink as they're too small a diameter and on the S they caused pain in the palms plus throttle return springs are way to heavy compared to my Zukes. Have degenerated neck discs, thus possible nerve problems running down arms to hands if the ergos are too extreme. So I use GP's with a Throttle Rocker and I'm good to go on long trips. It takes quite a while for the heat to work its way through the GP's in dead of winter and they aren't quite as hot on High as naked grips, but that's no big deal as the MRA double bubble screen keeps direct wind blast off the knuckles. Only time I have to switch from the "holey" summer gloves to insulated winter ones is when temps start to hit 'bout 36deg and consistently riding at speeds above 60mph. Hope this helps.