As noted above, we have porta-potties being delivered to HIH HQ. If the need arises on the trail, wag-bags (Ozark Trail, Restop) and a cheap folding pottie work best. Please don't lay one down on the trail. It takes a long time for that stuff to go away and it's not the most sanitary option. Wag-bag's can be used, sealed shut and tossed in the next guys Trasharoo as a prize for being the closest to you.
They make wag-bags specifically for #1 or #2. At HIH 3, a guy unfamiliar with wag-bags managed to get a #2 in a #1 bag, I'm not even sure how.

Proper kit. The bumper dumper! A must for all Landcruiser owners!!!