People tow trailers all the time with large truck campers. You just need a hitch extension. I used one that was 48" long to pull my boat behind my 11' long TC. SuperHitch and their SuperTruss are the leading manufacturer of this type of system but there are others.
I agree, a Capri camper is probably your best bet for finding a small one with a shower. Otherwise, 6.5' campers almost don't exist and certainly not with showers. Your widest variety of campers will be around 8' long if you want a shower on a short bed truck.
