I’m not so sure that “elohim” is ever translated as “judge” in the Septuagint. The 3-letter root for “judge” in Hebrew is “שפט” (shft); so we get “mishpat” for “judgment”, and “shfatim” for “judges”.
The Greek word for “judge” is “o κρινων” (krinon).
In the selections from Exodus and Samuel that you mentioned, “elohim” is translated as “kyrie” or “theos” (“lord” or “god”), never as “krinon”. And Psalm 82 is consistent in that vein as well.
Put briefly, the word “judge” does exist in the Septuagint, but I don’t think it’s ever used to translate “elohim”.
I just did a brief search, but if you want to try for yourself, go to
unboundbible.com/, and use "Greek OT: LXX [A] Unaccented as your first selection, Hebrew OT: WLC (Consonants & Vowels) as your second, and then pick an English translation of your choice as the third. Then, search within “Old Testament” for “κριν%” to get all forms of the Greek root for “judge”. Then, see if any of them correspond to “elohim”.
Let me know if you come up with anything; this is an intersting exercise.
κριν%