Depends on what part of the country you are in as to what dealers get for stock cars. Have them look on their computer for cars configured to your options. They will all have the silly Preferred Package.
Go on lexus.com, and "Build" your IS. If you put in your zip code, you will see the choice of "packages" that are delivered to your region. If you don't see it, that means it will be near impossible to "find" one, and you may want to special order, or reach out to a dealer in another area of the country if they deliver cars that way elsewhere.