Try a thin coating of Quad Seal. It will glue it on and keep water out. Remember, thin and on the outside, not inside or you will never get them off again without breaking them.
Put a tiny bead and quickly smear it over the edge with an oiled finger. WD 40 works, but I have a drop of oil on a paper so I can keep re-wetting your finger so it won't stick to you.
2017 SLX 195RB
2014 Jeep Grand Cherokee Overland, gas 3.7 V6
Andersen WDH hitch
Dometic Milenco Aero mirrors