Your raft looks in good shape. Perfect two person craft.
You likely don't need a new frame. Just find someone to fabricate a frame section with an anchor system for the back of the boat. Add a couple of d-rings, lash it to your frame and boat with a couple of straps and your good to go.
The frame is made of steel. Heavy as hell. The seats are old treated wood, the frame probably weighs about 50-60 pounds. A little excessive. It is completely hand made. Those are tennis balls on the corners held on with gorilla tape. The frame is also held together with gorilla tape.