it has been some time, but remember seeing a porta potty, being hauled on same trailer with a skid steer. it was a landscaping business. and some attachments here and there on the trailer as well.
for the ladies, its opening side door of truck and squatting. and tissue into a generic plastic bag ya get your groceries in.
i was laughing pretty hard, but remember seeing some sort of funnel, for the ladies to pea standing up per say.
5 gallon bucket with bag, a fold up lawn chair, with bottom cut out, has been used here a few times for the ladies 1 / 2 / tampons / pads.
besides toilet paper, have some of them oh what are those stupid things, sanitation wipes (kinda of a soapy towel) ya pull out of a plastic container. ((baby / diaper area most likely in a store)) having the individual towel in a foil wrapping (condom wrapping per say) for quick access without having to dig out a soapy wet slippery towel from a plastic container helps
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if in town, most likely it is a quick drive to local gas station for bathroom break, or fast food restaurant.