Well, I didn't think we'd get anything productive done with our rig, while I'm in Japan. But, I had some time to wander the local home center store and look at appliances and shower wands. Since many of the bathrooms and kitchens here are small, the scale works for some of our vehicles. They have these cool little two-burner cooktops with a small center broiling/baking tray (it's the little door in the center).
Well, we're not getting one of the cooktops. But, always thinking (that's scary, sometimes) I went to the other section where they carry cookware. I remembered seeing mention of small baking trays, as a possible option for creating a recessed emergency light replacement. Those little broiler/baking trays are small... hmmm, might the cookware work? What do you know, they have tiny shallow bakeware in both stainless and aluminum. Size looks close... note measurements... they're metric, of course.
I took photos, then went back to my hotel. I have no phone data coverage here, so I looked up the installation instructions for my Whelen 9E lights and the opening is... drum roll... well, it's 8.7 inches wide, by 6.45 inches tall. Convert to metric and that's 221mm wide by 164mm tall. So, it looks like these are darn close... large enough to be sure they'll cover the opening, but not so big that they require much cutting or look garish.
I ended up buying the 4 aluminum ones they have on the shelf, and ordering 6 more. Those will be here (I'm in Goshogawara, Japan) on Wednesday, and that will give me enough to replace the 8 side lights and the 2 rear white scene lights.
I'll most likely mount them, with good sealant of course, using some small sheet metal screws in the side walls of the pans, so they catch the backside of the skin and trap the pan in place. After we paint the box, and the pans, I'll caulk around the pans so that rolled lip ends up more tapered. I think they'll look fine, with lights inside them. Wires, through grommets, will power an LED light in each pan. They won't be totally recessed, but they won't protrude a ton either. I'll probably go with one of these, off Amazon - decent ratings and affordable:
From a purely stupid "that will probably look better" perspective, the wider 6.5-inch lights would probably look better.
But, I think the smaller (cheaper) ones will give plenty of light - enough, that we'll most likely switch these in pairs so we don't have to have all 4 on at once, if we don't want that much light.