You mentioned a wheelchair lift for your van, and I'm not sure if you have mobility issues and how that complicated peeing outside. I tell me sons the best kind of pee is a nature pee and will even pee outside of my apartment building or near a portapotty as long as it's undercover and won't leave any trace other than a wet mark in the ground. It's one of the privileges of being a man, so I will exercise my right to pee freely as long as I'm not offending anyone or doing anything illegal.
I usually will find a tree or bush to take care of mother nature's call but in the event that isn't possible I use a coffee can with a snap tight lid such as Folgers or Maxwell House. This not only prevents unfortunate spills it also contains the odor. To avoid any mixups I use a magic marker and write P on the lid and on the sides of the can. When it is convenient I empty and rinse out the can for later use.