Most any major auto parts store such as NAPA, Carquest, Advabced Auto, etc, that carry any of the Meguiars prducts can order it for you if they don't stock it. My local NAPA dealer got it in one day for me.
Are you able to order it directly from Meguiar's? Or is the shipping pretty high? You can also check their website for "authorized dealers" or something. That might give you a few places to try. Though, it seems that it isn't very complete because there are places near me that sell the whole Meg's line yet don't show up in that search.