Thank you all very much for your answers, the thing is that, I am trying by all means to preserve the original leather, the only seat that is damaged is the driver's, the rest of the seats are correct, I know that if I find a seat in color cognac, it's not going to be exactly the same as mine but then as a step two, I'll have to make them all look the same, but the most important thing is to find original leather in that color so I can keep the original seats.
I have already found the back of the driver's seat. A friend from Holland sold it to me, now I'm missing the driver's seat where you sit.
My other option is to use the leftover leather from the old backrest and try to put it in place of the seat, but it's all theory until I have it in front of me. I won't see if I can do it. Obviously all this will be done by an experienced person, a professional, not me. The option of buying all new original leather is always interesting, but we are talking about a lot more money and I would honestly like to maintain the originality as much as I can.
A big hug for everyone and thank you very much for your answers and ideas, which are undoubtedly always welcome.
Carl