At the u-pull-it yard where all the saturns are lined up.
If you want new, go to www.rockauto.com, look under suspension, Strut Assemblies.
Powertrain issues have many vehicles going to the scrap, so theres a chance to save some complete assemblies that are recent or still in good repair. You would get them complete and you have to add up the charges to price them, because of the parts you actually get, but subtract the time and tool rental for the labor you save. I would question the time left in your vehicle's powertrain, and weigh the costs.
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