Have a look at Northstar Liberty or Laredo, or Lance 650.
If a popup truck camper is an alternative, look into a Northstar 850SC. Outfittermfg and Hallmark also
make bathroom models, but pricier.
All of these will work on a 3/4 ton with a 6.5' bed.
Bundutecusa is another manufacturer that comes to mind.
There are others.
Small does not necessarily mean inexpensive, though.
If you are looking to buy used, an older Lance 815 might be an option.
2014 Ford F350 XLT 6.2 SCLB + 2017 Northstar Arrow