There are options for the 5.5 bed, you just have to do a lot of research. I have most of my links saved at home, but here is two from memory that will work in a 5.5 bed.
try this link
I have been looking for a SCREW camper as well, but it is hard to find one cheap to fit a SCREW since they are so new (less then 10 years old).
Also, check out Palimino Brand. They have truck campers that collapse and are lighter. I will need something like one of these (extra light weight) because I am already towing a 5000 lb boat. You can do it in an f150, heck they make campers for Rangers, S10's, Dakota's Etc.