IMHO and FWIW...
We used RTV3145 (Dow Corning) to glue in bezel glasses on Aircraft instruments. However this is rather expensive...and you can get a cheaper alternative called
Loctite 5145 that is exactly the same as the clear version of the Dow Corning RTV.
Still it's not that cheap at $27 but it's an
Alkoxy cure not Acetoxy cure agent which is much better for the glass and less out-gassing.