Like Steve_D says - in Oz, Canada & USA they have a slightly different camping ethic. What your after is certainly not too much to ask for - for a trip where your camping from the car and not on a site with facilities. Otherwise you'd not only have to carry your waste until a suitable opportunity to dispose of it - You'd also have to carry your toilet frame. Mind you the frame needn't be heavy or big, maybe something fashioned from something like the one pictured. Or even consider the cardboard option through the link at; http://www.thebrowncorporation.com/

Sh it box.

With a bit of thought you could probably make one out of a cheap millets camping stool (ooer!) and some plastic bags  Or try the american/canadian sites, they are more geared towards carrying out their 'waste'  something I now do myself.

Steve D