try to find a metal strip that has a rounded t-profile like this:
Paint it in the bezel color and just plonk it loosely at an angle into the gap. When rotating the bezel, pull it out, rotate the bezel, put it back in.
There are also black rubber car trim strips like this, no painting required, no scratching (like metal) as they are soft and flexible, and they come in different sizes. Some come with adhesive strips attached, if you want to make it permanent. If still worried about scratching, just elevate the strip so it sits very slightly above the bezel.