You didn't describe what sort of damage the case has received. Based on the vintage and brand, I bet the case is wood, covered in some sort of cloth that is supposed to resemble leather. I have a couple of Underwood portables of this vintage with beat-up cases, and I think some sort of wood glue can help mend them if the wood is loose, or the joints (dovetailed on mine) are coming apart. But if the case is really falling apart, you may be out of luck. As for the fabric covering, that's probably of lesser importance, but you might be able to find some sort of contact paper with a similar look and feel that's self-adhesive.