bought a tetford potty 8 yrs ago would not drive with out one,when you need it empty go to flying j get an rv card empty it for 3.bucks worth every penny.
What you want that is quicker and cheaper than a huge portapotty in the cab is a 'Piddle Pail'.
It looks like a lunchbox and works perfectly and cleanly every single time. It's is for both men, women and kids.