So I finally got around to making the housing for the element... safety first (or not).
Here is what I did.
It is a cannibalized plastic box with an all weather face plate. The recessed outlet is sealed up with silicone and the box is fully plastic welded (plastic specific epoxy) to the keg exterior.
I used a profile guage to steal the profile of the keg:
Then, I traced that profile onto the box, and cut it out with my mini band saw.
Then I clamped the box in place with a bungie cord, and epoxied the crap out of it. Wiped smooth with a squeegee and bob's yer uncle.
The flash picks up some extra epoxy, but it looks perfect with the naked eye.