Wasn't there at least one book or graphic novel that depicted former Republic Clones who were still alive during the time of the Empire and the OT? [...]
Karen Traviss's Republic Commando
novel series ended with several clones living on Mandalore, having gone AWOL during the waning days of the Clone Wars. Her books in the Legacy of the Force
series somewhat picked up on some of those threads - namely, Boba Fett and Jaina Solo encountering one of those former clonetroopers, as well as the son of a Jedi and a clonetrooper.