How old are you? As the legs get older, a folding toilet seat gets very handy when there's no outhouse nearby. The bags they sell with them are a PIA. Dig a little hole and set the stool over it.
Rocky:
I use the toilet type that sits on top of a 5-gallon bucket. Yours is collapsable. That's an obvious space saving feature in a pickup that's full of stuff already. I fill my bucket with extra toilet paper, tall kitchen trash bags and a spray can of air freshener. So it doesn't take up too much extra space.
I also use one of those collapsable, spiral trash can thingys, into which I put leaf/garden bags.
KC