I'm going to be the outlier here and say that as a frequent traveler, I have had much better luck going through pat downs with my packer than putting it in my bag. In my bag it was always pulled out and passed around and laughed at. Now, I wear it through, I get read as male and therefore the thing in my pants causes no alarm.
I have an Emisil now. I love it. Very realistic. But in reality, you need confidence with your stp, not realism. No one is going to look that closely, and you can totally position yourself so that they see your back or your stream and not your "skin." You can swim with most real packers, just leave your shorts or underwear on. The river is a great time to get your undies clean anyway, so it's not a big deal that it's not naked time. No stp is going to pass a full naked scenario unfortunately, but you don't need to.
I had great luck with a plain medicine spoon and separate packer for a while. If you practice with it, you can get very confident and smooth and no one will notice. If you're going to swim, you'll definitely want something in your shorts though, as wet shorts make it very obvious if there is something there.