So as I understand it the plan is to buy a used camper for very little money. The camper needs to be small and light weight and then you will work on it to get it even lighter so the Tundra will be able to handle the load.
Getting a decent and appropriate used camper is likely to be more expensive than you want. Then there is all the work and frankly unless you strip everything out, the weight is likely to be more than the Tundra can and should handle. There are some choices for popup campers that might work but finding one is even more difficult since there are relative few popups sold to begin with.
Personally, I would forget the truck camper idea and look for a popup tent trailer in need of some work and loving care.
