There are a lot of Foresters in Tucson so just about any car dealer could have one or more on their lot but Tucson Subaru is likely your best source. Also, don't overlook the five Subaru dealers in Phoenix which is about two hours away. Just make sure you check a vehicle history report for the history of the car's registration location. Just because it's on a Tucson/Phoenix car lot doesn't mean it is a "local" car.
CarGurus does a good job of consolidating all used car listings: https://www.cargurus.com/
CarGurus does a good job of consolidating all used car listings: https://www.cargurus.com/