You can get them in the UK - they're £100, mind! Good job they don't make one small enough for a cocker spaniel. Thinking about the Kurgo Wander Pack now - it's mainly so he can carry bags of his own poo rather than making me lug them around...
I carry starch based poop bags for hiking. Pick it up in the bag and then find a nice secluded place away from water to bury it.