Hi Jim, I live in Florence and I usually have to buy film online...
Unfortunately the shop mentioned by "TheFlyingCamera" doesn't exist any longer...
BUT, only to limit myself to the central part of the city, you can find 120 films - BW and color - by BONGI, in Por Santa Maria, the road that leads to the Ponte Vecchio (here you can find a map)..
Hope this helps and enjoy these coooold days in Florence!
Damiano