There are some solid glass trims designed for wet areas, but none of them are air tight that I'm aware of. You might want to check with the manufacturer, but if you have access to the attic, maybe some foil duct tape on the seams would seal them up and not generate enough extra heat to trip the safety circuit. Note, the box itself might be tight, but if the hole in the ceiling isn't, you might notice that. The heat from the lamp can cause some insulation to outgas. It might diminish as it boils off all that it can.