I put a Pachmayr Diamond Pro J Frame grip on my 2" K6S. She now handles every 357 Magnum load I have tried and does it with accuracy and some comfort.
Of course, I had to send the gun back to Kimber after approximately 350 rounds of mostly 38 Special (prior to the new grip) because the striker ad broken.....yep, was ready to turn it into a battered paper weight.
Since the fix and the Pachmayr grip I have about 1400-1500 flawless rounds through it of mostly 357 Mag and I carry it as a back up. She is loaded right now with 158 gr Underwood Semi Wadcutters.
The grip was a little larger than the original, but makes the gun a heck of a lot more accurate to go along with the recoil control.
Kimber dropped the ball, IMHO, from the git go on the original grip and not making sure that there were alternative grips available.
The Controlled Core grip (Crimson Trace)was only on their newer produced guns unless it is being offered individually in the last month ish.
I had to put some stiff foam under the back strap of the pachmayr J frame grip and the back strap of the grip does not fully reach to the top of the gun's back strap. Otherwise it has worked very well for approx 1,000 - 1,100 rounds.