Back to the OP. They do make smaller lightweight 5th wheels you just need to find one that works for you. Keystone has one called the Couger Half-Ton that will work depending on your truck.
Most people here will tell you to get a new truck. That's fine if you are able to but if you want to keep your truck, you need to know what your trucks towing capacities are and then look for a trailer that will fit that. Since you didn't post anything about your truck there is no way of knowing what you can handle.
Another thing to be aware of is your bed length. If you have a short bed you will get close to the cab with the front cap of the camper when you turn tight.
Good luck.