OMG. This thread is too funny. But, as someone who both backpacks and sails (in a little cruiser that doesn't have a holding tank for its head), these things can be ... ah ... important.
Here's what we use on the boat, and it's quite successful. We have to store the waste in the head itself, and this does a fantastic job of containing odor for a whole week, even in summer.
http://www.campmor.com/outdoor/gear/Product___11129
If you just go to the Campmor home page and enter "toilet" in the search field, you'll find all sorts of cute pop-up sheds, tentettes, and other "waste management" ideas.
And you don't even have to admit you use them, unless another chaser happens to get pictures....
Sidebar: my son is in the Marines, currently deployed in Iraq, and he tells me they use a similar product. He has many highly inappropriate but funny stories about them, which I obviously can't share here, but use your imagination. Hint: "mistaken for seat cushion" is one.