There is an audio recording in existance from a California show in early August of 1997. Mike gives a little introduction to Carl right before they perform "God Only Knows". Carl then thanks his doctor's onstage and then dedicates "God Only Knows" to them. It is rather emotional. There's also a point in the show when Carl says that he had just being telling Mike(Mike Meros?) that it had been a great summer. I think this was only like a week or two before Carl had to leave the tour. Pictures also do exist from Carl's final performance (in Atlantic City?), but they have never been made public.
As I have posted elsewhere on this board, I was at that California show. August 3, 1997 at the Glen helen Pavilion in Devore, just outside LA. Carl sounded exceptional on GOK, SOS and his other leads. Spoke with him very briefly backstage, he was very bloated from the chemo, but all reports were that he was going to make it. I had no idea it would be that last time I would see or hear him live.