Several companies used to make small import campers. I had an Okanagan 7 foot that I had on the back of an 88 Ford Ranger and we actually camped in it regularly for 2 years with me my wife and our son and then did a couple trips with our daughter as an infant and 4 year old son. (ok THAT was cramped). Completely serviceable for a couple and quite comfortable for solo trips.
www.kenkraft.ca/#!camper-vans/c1co
http://www.northern-lite.com/truck_camper_lite_610.php
https://www.livinlite.com/truck-campers.php
http://www.northstarcampers.com/online-catalog.php?headerbar=0&view=prods&parentId=11&catId=12
That should get you started. :-)