The Tupperware suggestion sounds about the best idea to me, never thought of that, and it comes in all shapes and sizes, so it would be easy to find a piece that wouldn't appear too bulky in your backpack. Personally I just throw a bottle of cologne in my bag before the leaving d crib when I know I am going to be on the subway and/or bus with a package.

Got mi thinking bout going to the Tupperware route though, I'm usually on edge a bit when I'm out, not so much about the possible possession and intent charges but got warrants on top of that Should get some of that infomercial shit.. "the sound means it is airtight!"