First thing I usually do is dip the glass in Future. This will protect it from almost anything.
Then depending on the fit of the glass I would use either Testors Clear parts Cement, Regular Elmers glue, or a Tiny bit of Ca.
The Testors and Elmer's Glue can be used to fill any gaps you may have. Where as The Ca can be used if the fit is as tight as you like w/o any filling needed. The Future should protect the glass from fogging if regular Ca is used.
Hope this helps
Paul