Travel Lite makes a hard side camper with a shower/porta potty. Remove the porta potty and you have a nice sized shower stall. No grey tank, so you either have to be hooked up or drain into a tote. But very light weight for a SB truck.
Model 770R, not advertised much but is perfect for our family of 3. It's the same size as 770, but with a shower stall instead of the storage cabinet in the porta potty area.
Oh, it does hang over the back by about 4" (??). I'm going from memory... we run with the tailgate down and it covers a few inches of the tailgate with room to stand on the tailgate while entering the TC. We tow a heavy duty Cam trailer with no problem. No hitch extension.
PM me if you want any more info.