One of the coaters I liked was
http://www.jet-hot.com/Pages/coatings.html. They quoted around $350-400 for both a few years ago plus sent a cheesy video. Pricey, but the temperature range was pretty high. There are lots of companies, but get the specs.
Pelican also sells a inexpensive HeetSheet shield which helps protect the lower heads from radiating heat, but total enclosure is a sure bet.