@DoubleTreble@sewing I think it would be important to find a similar fabric. Changing sleeves isn’t easy. If you want to add a piece of fabric that has the same width everywhere, you’d have to detach it a bit from the shoulder and also change the cuff.
Avoid that by adding a piece that gets thinner at the end, but that’s definitely a hand sewing job then. That’s not a common clothes alteration, adding new sleeves might be easier and there are tutorials for that.