Renault Laguna II 5 gears replacement in 6 gears

Hello guys. Today I would have a bit of an extraordinary topic. I drive a Renault Laguna II 2001. This one has a five-speed manual transmission. As the speed is at 100 KMH at 3000 revolutions, I would like to have a sixth gear. Can anyone tell me if a transmission of another Laguna would fit in such a way to get a sixth gear. Of course, prefers an original Laguna II 6 gear. Also any other gearbox around the sixth gear finally Maybe someone can help me further. Now many people will say and think, buy you one with 6 gears. Yes I could do. However, this is the old car from my father, which he bought new times. Since he is always so happy when I travel by car, I hold it in honor.