@jimkanaris well that depends on where you purchase it from. You can get replacements from places [https://www.mobiledefenders.com/back-glass-with-adhesive-for-galaxy-note-20-ultra-oem-service-pack-mystic-bronze.html|like this] and many others. To work on your phone to repalce the cover use something like this guide [guide|142699|Samsung Galaxy Note20 Ultra Rear Camera Assembly Replacement - iFixit Repair Guide|new_window=true]
Cost about $USD 50 if you do it yourself. Now, if you want somebody else to do it, you really have to ask the places you have in mind. iFixit does not do repair. Here we ***''empower you''*** to fix your own device. You can get parts, great guides and free advice to assist you with this task which looks fairly straightforward.