It looks pretty easy to make... if nothing else a simple modification could be done to any standard hive body to add this feature... maybe even add insulation if you're that concerned about insulating your hive. Just build it like a standard house wall, only use 1x2's instead of 2x4's for the studs... make sure to cap both top and bottom... especially if adding insulation.
Anyway, wood is a pretty good insulator by itself, so I don't think I'll do this with any of my hives, but then again, I don't live up in the great frozen tundra like some of you do.