I drove a topless 1978 CJ5 as a daily driver for many years. I wrapped my insurance card and registration in a plastic bag and locked it in the center console. Cell phones did not exist yet and the glovebox was not an option as it housed a large stereo speaker.
Haven't looked under the seats in a Gladiator, but in the 2dr JL's there are vents & electronics and wiring that won't let you mount under seat lock boxes like they have for JK's. Haven't found anyone who makes under seat for JL based yet (has anyone else?). Miss having them, had 2 in the JK. They do make a locking steel door for under the console lid though.