Hi I'm assuming the case is an actual protective case and not the actual phone housing? If it's the prote time case and your referring to the front display section that usually has a small strip of adesive on the edge then I'd just remove the existing none sticky tape clean area with an alcohol wipe to remove residue and then cut and attach a new strip of thin double sided tape. Preferably a 3m brand for a longer lasting stick.
You have to buy a new case, Samsung don't sell the glue pads separately.
You could try finding double sided tape of the right thickness, or other case providers options. But Samsung don't sell an official version (I'm now on my third case in 2 years 🤬).
It's an absolute rip off. Samsung need to start selling the strips separately.