Lens on back shattered

If you are referring to the protective glass between the lens and the outside world, you certainly can.

Here is one vendor selling it: https://www.ebay.com/itm/304140055710

Or shop around to somewhere else. They can be bought in many places.

When replacing this glass, use a heat gun, iOpener, hair dryer, or other source of heat to loosen the adhesive. Carefully remove all glass shards, use a pair of tweezers to get any glass shards out from the cracks. Turn the phone over (NOT over your face! Over a trash can only!) and gently shake it for a couple minutes at all angles to give any small glass shards that may have fallen a chance to fall back out, and blow compressed air into it to help any stuck glass on it's way.

Remove any adhesive residue by peeling as much off with your tweezers as you can, and remove the rest with a q-tip dipped in 90%+ isopropyl alcohol. Use a clean, dry, nothing on it q-tip to remove any dust from the camera lenses carefully as the last step before putting the new protective glass on.

If your actual camera lenses have been damaged, your camera module(s) will need to be replaced to restore image quality. There is no way to fix a damaged lens without very delicate and technical repairs, and it honestly is not worth it versus the cost of replacing the camera.

Good luck!