Personally I think insoles are a good option if your foot is such that you need them in other shoes. I'm about as flat footed as they come and have been lucky enough to find shoes that fit and feel perfect (but it took a while to find them) Specialized S-Works. In your case if the shoes you had fit nicely, were comfortable and did not result in any foot pain, but have broken in to the point where they are too big maybe a cheap insole will fill in enough...