On my 1965 CJ-6, there is a glove box but it is made from cardboard....! They did'nt get it right away! It took times
Willys wasn't alone installing cardboard glove boxes. You will find them also in the 40's to 50's pickups and trucks. If you manage to keep them dry, they actually will last quite awhile. For a CJ 5/6, Quality Craft makes a nice ABS replacement.
As for Steve's box, one probably could mount something like that off the cowel seam and brace so you didn't have to drill through the exterior of the tub. Even a snap-lid kitchen storage container would work for the registration and proof of insurance.
If one isn't doing a factory restoration, the best solution is just to build a door similar to the MB/GPW version and box off the entire area to the firewall for the actual box. Something that will actually provide a lot of useable volume.