From Van With Porti-Potti to Truck?

Wasn't sure where to post this but have been trying to work it out in my head for some time. We have always had a van with TT or pop-up which gave us room for a porti-potti in the tow vehicle which with our crew, it really is needed since we have an adult son with Down syndrome who isn't the best "planner" in the world but at least, he is smaller and lean guy. So, I have been looking at trucks online and wondering if with the crew cab with the split seat, does anyone know if a small porti-potti would fit in the back? I know about the devices for urine and they are handy but looking for something more, well, you get the idea. So, I just had to ask since I haven't the courage yet to go look at trucks carrying the porti-potti along but if it looks like a possibility, I'm lug in it along on the shopping trip after a thorough cleaning of course.