I've decided that I'm just going to go with the JB Weld. I may even use the liquid type instead of the putty and basically trowel it on, basically pave the seam.
I did that with cracks on the ignition module on my first Subaru. It had cracked and I was having arcing in wet weather.
I dried everything out, paved the cracks, and it lasted another 2 or 3 years with no problems.
I only use the lantern when I'm on my back deck grilling or sitting out, and I use it with citronella lamp oil. Make the mosquitoes gag a little bit before the bore in for a strike.