Check: http://www.amazon.com/The-PETT%C2%99-Portable-Environmental-Toilet/dp/B001CWAIJI

That is the portable "toilet". However, one critical component is the enzyme that is used to render human waste to dumpster safe.

Rubicon Trail Foundation and California OHMVR began experimenting with that system several years ago. If you talk to the FOTR/RTF folks at the kiosks, they will recommend the package enzyme as the "best" solution.

You do not need the above noted toilet. A 5-gal home brew bucket will work.

You can buy the enzyme packs at most of the major sporting goods stores. I have seen them at Bass Pro Shop, Cabelas, and Big 5.

For more information, see: http://www.gocleanwaste.com/products