I actually (contrary to my usual) went the the website for the service department where I bought the car. They have a "tire finder" feature on the website, which includes an offer to match anyone's price (which I didn't need to invoke, since their prices were surprisingly competitive already). It had the P7s and about 35 other options.
http://www.selmanchevy.com/TireFinder
http://www.selmanchevy.com/TireFinder