Do you just put some silicone around the light, and press the rubber seal into it, or is there a special sealer that is used for this purpose? Epoxy? Etc?
I'd use a silicone-based adhesive that stays flexible and won't dry-out the rubber. That, or weatherstripping adhesive (but its yellow, IIRC). Epoxy may work too, but it wouldn't be my first choice.